From 9e61dd33a9468b77b72276e76d8f9957ce48f10b Mon Sep 17 00:00:00 2001
From: HenningWendtland <156231187+HenningWendtland@users.noreply.github.com>
Date: Mon, 15 Jun 2026 11:46:37 +0200
Subject: [PATCH 1/5] feat: ad bieannial and triannial billing frequency

---
 README.md                                     | 10 +--
 simple_subscription/locale/de.po              | 74 +++++++++--------
 simple_subscription/locale/main.pot           | 79 +++++++++++--------
 .../simple_subscription.js                    | 25 ++++++
 .../simple_subscription.json                  |  4 +-
 .../simple_subscription.py                    | 41 +++++++---
 .../test_simple_subscription.py               | 49 +++++++++++-
 7 files changed, 198 insertions(+), 84 deletions(-)

diff --git a/README.md b/README.md
index 99708c1..cd685aa 100644
--- a/README.md
+++ b/README.md
@@ -9,17 +9,17 @@ Easy setup: existing **Subscriptions** get copied from ERPNext (you have to canc
 3. Set a _Start Date_
 4. Select if billing is based on _calendar months_ or _Start Date_
 5. Select if billing is supposed to happen _at the beginning of period_ or _after end of period_
-4. Select a _Frequency_
-5. Add items to the table
-6. Select a _Sales Taxes and Charges Template_
-7. Click "Save"
+6. Select a _Frequency_ (_Biennial_ and _Triennial_ require billing based on _Start Date_)
+7. Add items to the table
+8. Select a _Sales Taxes and Charges Template_
+9. Click "Save"
 
 ### Actions
 
 - Submit a **Simple Subscription** to start generating invoices.
 
     - New invoices for the current period will automatically be generated once per day if they don't yet exist
-    - If you need an invoice immediately, click the button "Create current {Monthly / Quarterly / Yearly} invoice".
+    - If you need an invoice immediately, click the button "Create current {frequency} invoice".
 
 - Mark a **Simple Subscription** as _disabled_ to stop generating invoices.
 - Duplicate a disabled **Simple Subscription** to change any values.
diff --git a/simple_subscription/locale/de.po b/simple_subscription/locale/de.po
index 046c230..df5a709 100644
--- a/simple_subscription/locale/de.po
+++ b/simple_subscription/locale/de.po
@@ -7,7 +7,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: Simple Subscription VERSION\n"
 "Report-Msgid-Bugs-To: hallo@alyf.de\n"
-"POT-Creation-Date: 2024-12-02 17:26+0053\n"
+"POT-Creation-Date: 2026-06-15 11:45+0053\n"
 "PO-Revision-Date: 2024-12-02 17:26+0053\n"
 "Last-Translator: hallo@alyf.de\n"
 "Language: de\n"
@@ -16,7 +16,7 @@ msgstr ""
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=utf-8\n"
 "Content-Transfer-Encoding: 8bit\n"
-"Generated-By: Babel 2.13.1\n"
+"Generated-By: Babel 2.16.0\n"
 
 #. Name of a role
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
@@ -28,69 +28,80 @@ msgstr ""
 msgid "Accounts User"
 msgstr ""
 
-#. Label of a Link field in DocType 'Simple Subscription'
+#. Label of the amended_from (Link) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Amended From"
 msgstr ""
 
-#. Label of a Select field in DocType 'Simple Subscription'
+#. Option for the 'Frequency' (Select) field in DocType 'Simple Subscription'
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
+msgid "Biennial"
+msgstr "Zweijährlich"
+
+#. Label of the period_type (Select) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Billing Period is based on"
 msgstr "Rechnungsperiode basiert auf"
 
-#. Label of a Select field in DocType 'Simple Subscription'
+#. Label of the billing_time (Select) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Billing Time"
 msgstr "Rechnungszeit"
 
-#. Label of a Link field in DocType 'Simple Subscription'
+#. Label of the company (Link) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Company"
 msgstr "Unternehmen"
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js:32
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js:53
 msgid "Create current {0} invoice"
 msgstr "Aktuelle {0} Rechnung erstellen"
 
-#. Label of a Link field in DocType 'Simple Subscription'
+#. Label of the currency (Link) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Currency"
 msgstr ""
 
-#. Label of a Text Editor field in DocType 'Simple Subscription Item'
+#. Label of the current_description (Text Editor) field in DocType 'Simple
+#. Subscription Item'
 #: simple_subscription/simple_subscription/doctype/simple_subscription_item/simple_subscription_item.json
 msgid "Current Description"
 msgstr "Aktuelle Beschreibung"
 
-#. Label of a Currency field in DocType 'Simple Subscription Item'
+#. Label of the current_rate (Currency) field in DocType 'Simple Subscription
+#. Item'
 #: simple_subscription/simple_subscription/doctype/simple_subscription_item/simple_subscription_item.json
 msgid "Current Rate"
 msgstr "Aktueller Einzelpreis"
 
-#. Label of a Link field in DocType 'Simple Subscription'
+#. Label of the customer (Link) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Customer"
 msgstr ""
 
-#. Label of a Data field in DocType 'Simple Subscription'
+#. Label of the customer_name (Data) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Customer Name"
 msgstr ""
 
-#. Label of a Check field in DocType 'Simple Subscription'
+#. Label of the disabled (Check) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Disabled"
 msgstr ""
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:105
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:128
 msgid "Failed to create subscription invoice"
 msgstr "Fehler beim Erstellen der Abo-Rechnung"
 
-#. Label of a Select field in DocType 'Simple Subscription'
+#. Label of the frequency (Select) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Frequency"
 msgstr "Frequenz"
 
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:196
+msgid "Frequency {0} is only supported when billing period is based on start date."
+msgstr "Die Frequenz {0} ist nur verfügbar, wenn die Abrechnungsperiode auf dem Startdatum basiert."
+
 #. Option for the 'Frequency' (Select) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Halfyearly"
@@ -102,17 +113,17 @@ msgstr "Halbjährlich"
 msgid "Invoices will be generated for periods starting on or after this date."
 msgstr "Rechnungen werden für Perioden erstellt, die an oder nach diesem Datum beginnen."
 
-#. Label of a Link field in DocType 'Simple Subscription Item'
+#. Label of the item (Link) field in DocType 'Simple Subscription Item'
 #: simple_subscription/simple_subscription/doctype/simple_subscription_item/simple_subscription_item.json
 msgid "Item"
 msgstr ""
 
-#. Label of a Data field in DocType 'Simple Subscription Item'
+#. Label of the item_name (Data) field in DocType 'Simple Subscription Item'
 #: simple_subscription/simple_subscription/doctype/simple_subscription_item/simple_subscription_item.json
 msgid "Item Name"
 msgstr ""
 
-#. Label of a Table field in DocType 'Simple Subscription'
+#. Label of the items (Table) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Items"
 msgstr ""
@@ -122,19 +133,19 @@ msgstr ""
 msgid "Monthly"
 msgstr "Monatlich"
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:42
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:50
 msgid "Please amend Subscription {0} before creating a Sales Invoice."
 msgstr "Bitte ändern Sie das Abo {0} bevor Sie eine Rechnung erstellen."
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:36
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:44
 msgid "Please enable Subscription {0} before creating a Sales Invoice."
 msgstr "Bitte aktivieren Sie das Abo {0} bevor Sie eine Rechnung erstellen."
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:39
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:47
 msgid "Please submit Subscription {0} before creating a Sales Invoice."
 msgstr "Bitte buchen Sie das Abo {0} bevor Sie eine Rechnung erstellen."
 
-#. Label of a Float field in DocType 'Simple Subscription Item'
+#. Label of the qty (Float) field in DocType 'Simple Subscription Item'
 #: simple_subscription/simple_subscription/doctype/simple_subscription_item/simple_subscription_item.json
 msgid "Qty"
 msgstr ""
@@ -144,12 +155,7 @@ msgstr ""
 msgid "Quarterly"
 msgstr "Vierteljährlich"
 
-#. Linked DocType in Simple Subscription's connections
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
-msgid "Sales Invoice"
-msgstr ""
-
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:91
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:117
 msgid "Sales Invoice already exists for this period: {}"
 msgstr "Rechnung für diese Periode existiert bereits: {}"
 
@@ -161,7 +167,7 @@ msgstr ""
 #. Name of a DocType
 #. Label of a Link in the Simple Subscription Selling Workspace
 #. Label of a shortcut in the Simple Subscription Selling Workspace
-#: simple_subscription/config/desktop.py:10
+#: simple_subscription/config/desktop.py:11
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 #: simple_subscription/simple_subscription/workspace/simple_subscription_selling/simple_subscription_selling.json
 msgid "Simple Subscription"
@@ -177,7 +183,7 @@ msgstr "Einfacher Abo-Artikel"
 msgid "Simple Subscription Selling"
 msgstr "Vertrieb"
 
-#. Label of a Date field in DocType 'Simple Subscription'
+#. Label of the start_date (Date) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Start Date"
 msgstr ""
@@ -187,11 +193,16 @@ msgstr ""
 msgid "System Manager"
 msgstr ""
 
-#. Label of a Link field in DocType 'Simple Subscription'
+#. Label of the taxes_and_charges (Link) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Taxes and Charges"
 msgstr ""
 
+#. Option for the 'Frequency' (Select) field in DocType 'Simple Subscription'
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
+msgid "Triennial"
+msgstr "Dreijährlich"
+
 #. Option for the 'Frequency' (Select) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Yearly"
@@ -220,3 +231,4 @@ msgstr "Kalendermonate"
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "start date"
 msgstr "Startdatum"
+
diff --git a/simple_subscription/locale/main.pot b/simple_subscription/locale/main.pot
index 040419f..d3eac1f 100644
--- a/simple_subscription/locale/main.pot
+++ b/simple_subscription/locale/main.pot
@@ -1,20 +1,20 @@
 # Translations template for Simple Subscription.
-# Copyright (C) 2024 ALYF GmbH
+# Copyright (C) 2026 ALYF GmbH
 # This file is distributed under the same license as the Simple Subscription project.
-# FIRST AUTHOR <EMAIL@ADDRESS>, 2024.
+# FIRST AUTHOR <EMAIL@ADDRESS>, 2026.
 #
 msgid ""
 msgstr ""
 "Project-Id-Version: Simple Subscription VERSION\n"
 "Report-Msgid-Bugs-To: hallo@alyf.de\n"
-"POT-Creation-Date: 2024-12-02 17:26+0053\n"
-"PO-Revision-Date: 2024-12-02 17:26+0053\n"
+"POT-Creation-Date: 2026-06-15 11:45+0053\n"
+"PO-Revision-Date: 2026-06-15 11:45+0053\n"
 "Last-Translator: hallo@alyf.de\n"
 "Language-Team: hallo@alyf.de\n"
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=utf-8\n"
 "Content-Transfer-Encoding: 8bit\n"
-"Generated-By: Babel 2.13.1\n"
+"Generated-By: Babel 2.16.0\n"
 
 #. Name of a role
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
@@ -26,69 +26,80 @@ msgstr ""
 msgid "Accounts User"
 msgstr ""
 
-#. Label of a Link field in DocType 'Simple Subscription'
+#. Label of the amended_from (Link) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Amended From"
 msgstr ""
 
-#. Label of a Select field in DocType 'Simple Subscription'
+#. Option for the 'Frequency' (Select) field in DocType 'Simple Subscription'
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
+msgid "Biennial"
+msgstr ""
+
+#. Label of the period_type (Select) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Billing Period is based on"
 msgstr ""
 
-#. Label of a Select field in DocType 'Simple Subscription'
+#. Label of the billing_time (Select) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Billing Time"
 msgstr ""
 
-#. Label of a Link field in DocType 'Simple Subscription'
+#. Label of the company (Link) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Company"
 msgstr ""
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js:32
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js:53
 msgid "Create current {0} invoice"
 msgstr ""
 
-#. Label of a Link field in DocType 'Simple Subscription'
+#. Label of the currency (Link) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Currency"
 msgstr ""
 
-#. Label of a Text Editor field in DocType 'Simple Subscription Item'
+#. Label of the current_description (Text Editor) field in DocType 'Simple
+#. Subscription Item'
 #: simple_subscription/simple_subscription/doctype/simple_subscription_item/simple_subscription_item.json
 msgid "Current Description"
 msgstr ""
 
-#. Label of a Currency field in DocType 'Simple Subscription Item'
+#. Label of the current_rate (Currency) field in DocType 'Simple Subscription
+#. Item'
 #: simple_subscription/simple_subscription/doctype/simple_subscription_item/simple_subscription_item.json
 msgid "Current Rate"
 msgstr ""
 
-#. Label of a Link field in DocType 'Simple Subscription'
+#. Label of the customer (Link) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Customer"
 msgstr ""
 
-#. Label of a Data field in DocType 'Simple Subscription'
+#. Label of the customer_name (Data) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Customer Name"
 msgstr ""
 
-#. Label of a Check field in DocType 'Simple Subscription'
+#. Label of the disabled (Check) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Disabled"
 msgstr ""
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:105
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:128
 msgid "Failed to create subscription invoice"
 msgstr ""
 
-#. Label of a Select field in DocType 'Simple Subscription'
+#. Label of the frequency (Select) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Frequency"
 msgstr ""
 
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:196
+msgid "Frequency {0} is only supported when billing period is based on start date."
+msgstr ""
+
 #. Option for the 'Frequency' (Select) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Halfyearly"
@@ -100,17 +111,17 @@ msgstr ""
 msgid "Invoices will be generated for periods starting on or after this date."
 msgstr ""
 
-#. Label of a Link field in DocType 'Simple Subscription Item'
+#. Label of the item (Link) field in DocType 'Simple Subscription Item'
 #: simple_subscription/simple_subscription/doctype/simple_subscription_item/simple_subscription_item.json
 msgid "Item"
 msgstr ""
 
-#. Label of a Data field in DocType 'Simple Subscription Item'
+#. Label of the item_name (Data) field in DocType 'Simple Subscription Item'
 #: simple_subscription/simple_subscription/doctype/simple_subscription_item/simple_subscription_item.json
 msgid "Item Name"
 msgstr ""
 
-#. Label of a Table field in DocType 'Simple Subscription'
+#. Label of the items (Table) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Items"
 msgstr ""
@@ -120,19 +131,19 @@ msgstr ""
 msgid "Monthly"
 msgstr ""
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:42
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:50
 msgid "Please amend Subscription {0} before creating a Sales Invoice."
 msgstr ""
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:36
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:44
 msgid "Please enable Subscription {0} before creating a Sales Invoice."
 msgstr ""
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:39
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:47
 msgid "Please submit Subscription {0} before creating a Sales Invoice."
 msgstr ""
 
-#. Label of a Float field in DocType 'Simple Subscription Item'
+#. Label of the qty (Float) field in DocType 'Simple Subscription Item'
 #: simple_subscription/simple_subscription/doctype/simple_subscription_item/simple_subscription_item.json
 msgid "Qty"
 msgstr ""
@@ -142,12 +153,7 @@ msgstr ""
 msgid "Quarterly"
 msgstr ""
 
-#. Linked DocType in Simple Subscription's connections
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
-msgid "Sales Invoice"
-msgstr ""
-
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:91
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:117
 msgid "Sales Invoice already exists for this period: {}"
 msgstr ""
 
@@ -159,7 +165,7 @@ msgstr ""
 #. Name of a DocType
 #. Label of a Link in the Simple Subscription Selling Workspace
 #. Label of a shortcut in the Simple Subscription Selling Workspace
-#: simple_subscription/config/desktop.py:10
+#: simple_subscription/config/desktop.py:11
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 #: simple_subscription/simple_subscription/workspace/simple_subscription_selling/simple_subscription_selling.json
 msgid "Simple Subscription"
@@ -175,7 +181,7 @@ msgstr ""
 msgid "Simple Subscription Selling"
 msgstr ""
 
-#. Label of a Date field in DocType 'Simple Subscription'
+#. Label of the start_date (Date) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Start Date"
 msgstr ""
@@ -185,11 +191,16 @@ msgstr ""
 msgid "System Manager"
 msgstr ""
 
-#. Label of a Link field in DocType 'Simple Subscription'
+#. Label of the taxes_and_charges (Link) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Taxes and Charges"
 msgstr ""
 
+#. Option for the 'Frequency' (Select) field in DocType 'Simple Subscription'
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
+msgid "Triennial"
+msgstr ""
+
 #. Option for the 'Frequency' (Select) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Yearly"
diff --git a/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js b/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js
index 9f89807..e0db830 100644
--- a/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js
+++ b/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js
@@ -1,6 +1,25 @@
 // Copyright (c) 2022, ALYF GmbH and contributors
 // For license information, please see license.txt
 
+const ALL_FREQUENCIES = ["Monthly", "Quarterly", "Halfyearly", "Yearly", "Biennial", "Triennial"];
+const START_DATE_ONLY_FREQUENCIES = ["Biennial", "Triennial"];
+
+function set_frequency_options(frm) {
+	const options =
+		frm.doc.period_type === "calendar months"
+			? ALL_FREQUENCIES.filter((frequency) => !START_DATE_ONLY_FREQUENCIES.includes(frequency))
+			: ALL_FREQUENCIES;
+
+	if (
+		frm.doc.period_type === "calendar months" &&
+		START_DATE_ONLY_FREQUENCIES.includes(frm.doc.frequency)
+	) {
+		frm.set_value("frequency", "");
+	}
+
+	frm.set_df_property("frequency", "options", options.join("\n"));
+}
+
 frappe.ui.form.on("Simple Subscription", {
 	setup: function (frm) {
 		frm.set_query("item", "items", function () {
@@ -21,7 +40,13 @@ frappe.ui.form.on("Simple Subscription", {
 		});
 	},
 
+	period_type: function (frm) {
+		set_frequency_options(frm);
+	},
+
 	refresh: function (frm) {
+		set_frequency_options(frm);
+
 		if (frm.doc.docstatus !== 1 || frm.doc.disabled === 1) return;
 
 		const translated_frequency = __(frm.doc.frequency, null, "Frequency of Subscription");
diff --git a/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json b/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
index 7fb27ab..8421d19 100644
--- a/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
+++ b/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
@@ -68,7 +68,7 @@
    "fieldname": "frequency",
    "fieldtype": "Select",
    "label": "Frequency",
-   "options": "Monthly\nQuarterly\nHalfyearly\nYearly"
+   "options": "Monthly\nQuarterly\nHalfyearly\nYearly\nBiennial\nTriennial"
   },
   {
    "fieldname": "section_break_5",
@@ -189,4 +189,4 @@
  "sort_order": "DESC",
  "states": [],
  "track_changes": 1
-}
\ No newline at end of file
+}
diff --git a/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py b/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py
index 93a2a30..0f1eb19 100644
--- a/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py
+++ b/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py
@@ -2,7 +2,6 @@
 # For license information, please see license.txt
 from datetime import date, timedelta
 from enum import Enum
-from typing import Union
 
 import frappe
 from dateutil.relativedelta import relativedelta
@@ -18,6 +17,11 @@ class Frequency(Enum):
 	Quarterly = 3
 	Halfyearly = 6
 	Yearly = 12
+	Biennial = 24
+	Triennial = 36
+
+
+START_DATE_ONLY_FREQUENCIES = frozenset({Frequency.Biennial, Frequency.Triennial})
 
 
 class PeriodType(Enum):
@@ -31,6 +35,9 @@ class BillingTime(Enum):
 
 
 class SimpleSubscription(Document):
+	def validate(self):
+		validate_start_date_only_frequencies(self.period_type, self.frequency)
+
 	def create_invoice(self, from_date: date, to_date: date) -> SalesInvoice:
 		msg = None
 		if self.disabled:
@@ -185,8 +192,25 @@ def get_from_and_to_date(
 		return get_calendar_period(current_period_start - timedelta(days=1), frequency)
 
 
+def get_start_date_only_frequency_error_message(frequency: str) -> str:
+	return _(
+		"Frequency {0} is only supported when billing period is based on start date."
+	).format(_(frequency, context="Frequency of Subscription"))
+
+
+def validate_start_date_only_frequencies(period_type: str, frequency: str) -> None:
+	if period_type != PeriodType.CalendarMonths.value or not frequency:
+		return
+
+	if Frequency[frequency] in START_DATE_ONLY_FREQUENCIES:
+		frappe.throw(get_start_date_only_frequency_error_message(frequency))
+
+
 def get_calendar_period(eval_date: date, frequency: Frequency) -> tuple[date, date]:
 	"""Return the first day and last day of the period containing `from_date`."""
+	if frequency in START_DATE_ONLY_FREQUENCIES:
+		frappe.throw(get_start_date_only_frequency_error_message(frequency.name))
+
 	invoice_month_map = {
 		Frequency.Monthly: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12],
 		Frequency.Quarterly: [1, 1, 1, 4, 4, 4, 7, 7, 7, 10, 10, 10],
@@ -207,22 +231,17 @@ def get_calendar_period(eval_date: date, frequency: Frequency) -> tuple[date, da
 
 
 def get_date_period(eval_date: date, frequency: Frequency, initial_date: date) -> tuple[date, date]:
-	no_of_month_map = {
-		Frequency.Monthly: 1,
-		Frequency.Quarterly: 3,
-		Frequency.Halfyearly: 6,
-		Frequency.Yearly: 12,
-	}
+	months = frequency.value
 
 	delta = relativedelta(eval_date, initial_date)
 
 	# determine no of period eval_date lies in when starting on initial_date
 	if eval_date >= initial_date:
-		month_detla_floor = (delta.years * 12 + delta.months) // no_of_month_map[frequency]
+		month_detla_floor = (delta.years * 12 + delta.months) // months
 	else:
-		month_detla_floor = (delta.years * 12 + delta.months - 1) // no_of_month_map[frequency]
+		month_detla_floor = (delta.years * 12 + delta.months - 1) // months
 
-	from_date = initial_date + relativedelta(months=(no_of_month_map[frequency] * month_detla_floor))
-	to_date = from_date + relativedelta(months=no_of_month_map[frequency]) - relativedelta(days=1)
+	from_date = initial_date + relativedelta(months=(months * month_detla_floor))
+	to_date = from_date + relativedelta(months=months) - relativedelta(days=1)
 
 	return from_date, to_date
diff --git a/simple_subscription/simple_subscription/doctype/simple_subscription/test_simple_subscription.py b/simple_subscription/simple_subscription/doctype/simple_subscription/test_simple_subscription.py
index a6e44b9..10ad20d 100644
--- a/simple_subscription/simple_subscription/doctype/simple_subscription/test_simple_subscription.py
+++ b/simple_subscription/simple_subscription/doctype/simple_subscription/test_simple_subscription.py
@@ -1,10 +1,11 @@
 # Copyright (c) 2022, ALYF GmbH and Contributors
 # See license.txt
 
-# import frappe
 import unittest
 from datetime import date
 
+import frappe
+
 from .simple_subscription import (
 	BillingTime,
 	Frequency,
@@ -12,6 +13,7 @@
 	get_calendar_period,
 	get_date_period,
 	get_from_and_to_date,
+	validate_start_date_only_frequencies,
 )
 
 
@@ -55,6 +57,31 @@ def test_get_date_period(self):
 		self.assertEqual(from_date, date(2022, 6, 25))
 		self.assertEqual(to_date, date(2023, 6, 24))
 
+		from_date, to_date = get_date_period(eval_date, Frequency.Biennial, initial_date)
+		self.assertEqual(from_date, date(2022, 6, 25))
+		self.assertEqual(to_date, date(2024, 6, 24))
+
+		from_date, to_date = get_date_period(eval_date, Frequency.Triennial, initial_date)
+		self.assertEqual(from_date, date(2022, 6, 25))
+		self.assertEqual(to_date, date(2025, 6, 24))
+
+	def test_get_calendar_period_unsupported_frequencies(self):
+		with self.assertRaises(frappe.ValidationError):
+			get_calendar_period(date(2022, 11, 7), Frequency.Biennial)
+
+		with self.assertRaises(frappe.ValidationError):
+			get_calendar_period(date(2022, 11, 7), Frequency.Triennial)
+
+	def test_validate_start_date_only_frequencies(self):
+		with self.assertRaises(frappe.ValidationError):
+			validate_start_date_only_frequencies("calendar months", "Biennial")
+
+		with self.assertRaises(frappe.ValidationError):
+			validate_start_date_only_frequencies("calendar months", "Triennial")
+
+		validate_start_date_only_frequencies("start date", "Biennial")
+		validate_start_date_only_frequencies("calendar months", "Yearly")
+
 	def test_get_from_and_to_date(self):
 		from_date, to_date = get_from_and_to_date(
 			frequency=Frequency.Monthly,
@@ -106,3 +133,23 @@ def test_get_from_and_to_date(self):
 		)
 		self.assertEqual(from_date, date(2022, 10, 5))
 		self.assertEqual(to_date, date(2022, 11, 4))
+
+		from_date, to_date = get_from_and_to_date(
+			frequency=Frequency.Biennial,
+			period_type=PeriodType.StartDate,
+			billing_time=BillingTime.AtBeginningOfPeriod,
+			eval_date=date(2024, 11, 7),
+			start_date=date(2022, 6, 25),
+		)
+		self.assertEqual(from_date, date(2024, 6, 25))
+		self.assertEqual(to_date, date(2026, 6, 24))
+
+		from_date, to_date = get_from_and_to_date(
+			frequency=Frequency.Triennial,
+			period_type=PeriodType.StartDate,
+			billing_time=BillingTime.AfterEndOfPeriod,
+			eval_date=date(2026, 1, 1),
+			start_date=date(2022, 6, 25),
+		)
+		self.assertEqual(from_date, date(2022, 6, 25))
+		self.assertEqual(to_date, date(2025, 6, 24))

From f12ef6b94a0a311e10dc4aa858ba20147794ca0b Mon Sep 17 00:00:00 2001
From: HenningWendtland <156231187+HenningWendtland@users.noreply.github.com>
Date: Mon, 15 Jun 2026 11:59:24 +0200
Subject: [PATCH 2/5] chore: apply auto-created .json changes

---
 .../doctype/simple_subscription/simple_subscription.json    | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json b/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
index 8421d19..4c0d406 100644
--- a/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
+++ b/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
@@ -1,5 +1,6 @@
 {
  "actions": [],
+ "allow_bulk_edit": 1,
  "autoname": "ABO-.#####",
  "creation": "2022-02-04 16:13:31.955134",
  "doctype": "DocType",
@@ -133,11 +134,11 @@
    "link_fieldname": "simple_subscription"
   }
  ],
- "modified": "2024-09-12 12:54:00.717315",
+ "modified": "2026-06-15 11:53:49.870013",
  "modified_by": "Administrator",
  "module": "Simple Subscription",
  "name": "Simple Subscription",
- "naming_rule": "Expression (old style)",
+ "naming_rule": "Expression",
  "owner": "Administrator",
  "permissions": [
   {
@@ -185,6 +186,7 @@
    "write": 1
   }
  ],
+ "row_format": "Dynamic",
  "sort_field": "modified",
  "sort_order": "DESC",
  "states": [],

From f4c0026fd126c7260b238818070de5168d6c51c0 Mon Sep 17 00:00:00 2001
From: HenningWendtland <156231187+HenningWendtland@users.noreply.github.com>
Date: Tue, 16 Jun 2026 11:35:49 +0200
Subject: [PATCH 3/5] feat: implement biennial and trieannial for calendar
 period

---
 README.md                                     |  2 +-
 .../simple_subscription.js                    | 25 ------
 .../simple_subscription.py                    | 72 +++++++++--------
 .../test_simple_subscription.py               | 79 ++++++++++++++-----
 4 files changed, 100 insertions(+), 78 deletions(-)

diff --git a/README.md b/README.md
index cd685aa..00aa1e6 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,7 @@ Easy setup: existing **Subscriptions** get copied from ERPNext (you have to canc
 3. Set a _Start Date_
 4. Select if billing is based on _calendar months_ or _Start Date_
 5. Select if billing is supposed to happen _at the beginning of period_ or _after end of period_
-6. Select a _Frequency_ (_Biennial_ and _Triennial_ require billing based on _Start Date_)
+6. Select a _Frequency_
 7. Add items to the table
 8. Select a _Sales Taxes and Charges Template_
 9. Click "Save"
diff --git a/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js b/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js
index e0db830..9f89807 100644
--- a/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js
+++ b/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js
@@ -1,25 +1,6 @@
 // Copyright (c) 2022, ALYF GmbH and contributors
 // For license information, please see license.txt
 
-const ALL_FREQUENCIES = ["Monthly", "Quarterly", "Halfyearly", "Yearly", "Biennial", "Triennial"];
-const START_DATE_ONLY_FREQUENCIES = ["Biennial", "Triennial"];
-
-function set_frequency_options(frm) {
-	const options =
-		frm.doc.period_type === "calendar months"
-			? ALL_FREQUENCIES.filter((frequency) => !START_DATE_ONLY_FREQUENCIES.includes(frequency))
-			: ALL_FREQUENCIES;
-
-	if (
-		frm.doc.period_type === "calendar months" &&
-		START_DATE_ONLY_FREQUENCIES.includes(frm.doc.frequency)
-	) {
-		frm.set_value("frequency", "");
-	}
-
-	frm.set_df_property("frequency", "options", options.join("\n"));
-}
-
 frappe.ui.form.on("Simple Subscription", {
 	setup: function (frm) {
 		frm.set_query("item", "items", function () {
@@ -40,13 +21,7 @@ frappe.ui.form.on("Simple Subscription", {
 		});
 	},
 
-	period_type: function (frm) {
-		set_frequency_options(frm);
-	},
-
 	refresh: function (frm) {
-		set_frequency_options(frm);
-
 		if (frm.doc.docstatus !== 1 || frm.doc.disabled === 1) return;
 
 		const translated_frequency = __(frm.doc.frequency, null, "Frequency of Subscription");
diff --git a/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py b/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py
index 0f1eb19..db2fca8 100644
--- a/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py
+++ b/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py
@@ -21,7 +21,14 @@ class Frequency(Enum):
 	Triennial = 36
 
 
-START_DATE_ONLY_FREQUENCIES = frozenset({Frequency.Biennial, Frequency.Triennial})
+MULTI_YEAR_FREQUENCIES = frozenset({Frequency.Biennial, Frequency.Triennial})
+
+INVOICE_MONTH_MAP: dict[Frequency, list[int]] = {
+	Frequency.Monthly: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12],
+	Frequency.Quarterly: [1, 1, 1, 4, 4, 4, 7, 7, 7, 10, 10, 10],
+	Frequency.Halfyearly: [1, 1, 1, 1, 1, 1, 7, 7, 7, 7, 7, 7],
+	Frequency.Yearly: [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
+}
 
 
 class PeriodType(Enum):
@@ -36,7 +43,7 @@ class BillingTime(Enum):
 
 class SimpleSubscription(Document):
 	def validate(self):
-		validate_start_date_only_frequencies(self.period_type, self.frequency)
+		validate_calendar_frequencies(self.period_type, self.frequency, self.start_date)
 
 	def create_invoice(self, from_date: date, to_date: date) -> SalesInvoice:
 		msg = None
@@ -165,7 +172,8 @@ def get_from_and_to_date(
 	:param eval_date: Date to evaluate the period for
 	:param period_type: Type of period to evaluate, defaults to CalendarMonths
 	:param billing_time: Time to bill the subscription, defaults to AfterEndOfPeriod
-	:param start_date: Start date of the subscription, required only for PeriodType.StartDate
+	:param start_date: Start date of the subscription, required for PeriodType.StartDate
+		and for multi-year frequencies with calendar months
 	"""
 	if period_type == PeriodType.StartDate and not start_date:
 		raise ValueError("start_date is required for period_type 'start date'")
@@ -186,47 +194,43 @@ def get_from_and_to_date(
 			start_date,
 		)
 	elif period_type == PeriodType.CalendarMonths and billing_time == BillingTime.AtBeginningOfPeriod:
-		return get_calendar_period(eval_date, frequency)
+		return get_calendar_period(eval_date, frequency, start_date)
 	elif period_type == PeriodType.CalendarMonths and billing_time == BillingTime.AfterEndOfPeriod:
-		current_period_start, _ = get_calendar_period(eval_date, frequency)
-		return get_calendar_period(current_period_start - timedelta(days=1), frequency)
-
-
-def get_start_date_only_frequency_error_message(frequency: str) -> str:
-	return _(
-		"Frequency {0} is only supported when billing period is based on start date."
-	).format(_(frequency, context="Frequency of Subscription"))
+		current_period_start, _ = get_calendar_period(eval_date, frequency, start_date)
+		return get_calendar_period(current_period_start - timedelta(days=1), frequency, start_date)
 
 
-def validate_start_date_only_frequencies(period_type: str, frequency: str) -> None:
+def validate_calendar_frequencies(period_type: str, frequency: str, start_date: date | None) -> None:
 	if period_type != PeriodType.CalendarMonths.value or not frequency:
 		return
 
-	if Frequency[frequency] in START_DATE_ONLY_FREQUENCIES:
-		frappe.throw(get_start_date_only_frequency_error_message(frequency))
-
+	if Frequency[frequency] in MULTI_YEAR_FREQUENCIES and not start_date:
+		frappe.throw(
+			_("Start Date is required for frequency {0}.").format(
+				_(frequency, context="Frequency of Subscription")
+			)
+		)
 
-def get_calendar_period(eval_date: date, frequency: Frequency) -> tuple[date, date]:
-	"""Return the first day and last day of the period containing `from_date`."""
-	if frequency in START_DATE_ONLY_FREQUENCIES:
-		frappe.throw(get_start_date_only_frequency_error_message(frequency.name))
 
-	invoice_month_map = {
-		Frequency.Monthly: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12],
-		Frequency.Quarterly: [1, 1, 1, 4, 4, 4, 7, 7, 7, 10, 10, 10],
-		Frequency.Halfyearly: [1, 1, 1, 1, 1, 1, 7, 7, 7, 7, 7, 7],
-		Frequency.Yearly: [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
-	}
-	no_of_month_map = {
-		Frequency.Monthly: 1,
-		Frequency.Quarterly: 3,
-		Frequency.Halfyearly: 6,
-		Frequency.Yearly: 12,
-	}
+def get_calendar_period(
+	eval_date: date, frequency: Frequency, start_date: date | None = None
+) -> tuple[date, date]:
+	"""Return the first and last day of the calendar period containing `eval_date`."""
+	if frequency in MULTI_YEAR_FREQUENCIES and not start_date:
+		frappe.throw(
+			_("Start Date is required for frequency {0}.").format(
+				_(frequency.name, context="Frequency of Subscription")
+			)
+		)
 
-	from_date = eval_date.replace(day=1, month=invoice_month_map[frequency][eval_date.month - 1])
-	to_date = from_date + relativedelta(months=no_of_month_map[frequency]) - relativedelta(days=1)
+	if frequency in MULTI_YEAR_FREQUENCIES:
+		years_span = frequency.value // 12
+		block_start_year = start_date.year + ((eval_date.year - start_date.year) // years_span) * years_span
+		from_date = date(block_start_year, 1, 1)
+	else:
+		from_date = eval_date.replace(day=1, month=INVOICE_MONTH_MAP[frequency][eval_date.month - 1])
 
+	to_date = from_date + relativedelta(months=frequency.value) - relativedelta(days=1)
 	return from_date, to_date
 
 
diff --git a/simple_subscription/simple_subscription/doctype/simple_subscription/test_simple_subscription.py b/simple_subscription/simple_subscription/doctype/simple_subscription/test_simple_subscription.py
index 10ad20d..b48834e 100644
--- a/simple_subscription/simple_subscription/doctype/simple_subscription/test_simple_subscription.py
+++ b/simple_subscription/simple_subscription/doctype/simple_subscription/test_simple_subscription.py
@@ -13,7 +13,7 @@
 	get_calendar_period,
 	get_date_period,
 	get_from_and_to_date,
-	validate_start_date_only_frequencies,
+	validate_calendar_frequencies,
 )
 
 
@@ -37,6 +37,46 @@ def test_get_calendar_period(self):
 		self.assertEqual(from_date, date(2022, 1, 1))
 		self.assertEqual(to_date, date(2022, 12, 31))
 
+		start_date = date(2022, 6, 25)
+
+		from_date, to_date = get_calendar_period(date(2022, 11, 7), Frequency.Biennial, start_date)
+		self.assertEqual(from_date, date(2022, 1, 1))
+		self.assertEqual(to_date, date(2023, 12, 31))
+
+		from_date, to_date = get_calendar_period(date(2023, 6, 15), Frequency.Biennial, start_date)
+		self.assertEqual(from_date, date(2022, 1, 1))
+		self.assertEqual(to_date, date(2023, 12, 31))
+
+		from_date, to_date = get_calendar_period(date(2024, 3, 1), Frequency.Biennial, start_date)
+		self.assertEqual(from_date, date(2024, 1, 1))
+		self.assertEqual(to_date, date(2025, 12, 31))
+
+		from_date, to_date = get_calendar_period(date(2024, 6, 15), Frequency.Triennial, start_date)
+		self.assertEqual(from_date, date(2022, 1, 1))
+		self.assertEqual(to_date, date(2024, 12, 31))
+
+		from_date, to_date = get_calendar_period(date(2025, 1, 1), Frequency.Triennial, start_date)
+		self.assertEqual(from_date, date(2025, 1, 1))
+		self.assertEqual(to_date, date(2027, 12, 31))
+
+	def test_get_calendar_period_multi_year_requires_start_date(self):
+		with self.assertRaises(frappe.ValidationError):
+			get_calendar_period(date(2022, 11, 7), Frequency.Biennial)
+
+		with self.assertRaises(frappe.ValidationError):
+			get_calendar_period(date(2022, 11, 7), Frequency.Triennial)
+
+	def test_validate_calendar_frequencies(self):
+		with self.assertRaises(frappe.ValidationError):
+			validate_calendar_frequencies("calendar months", "Biennial", None)
+
+		with self.assertRaises(frappe.ValidationError):
+			validate_calendar_frequencies("calendar months", "Triennial", None)
+
+		validate_calendar_frequencies("calendar months", "Biennial", date(2022, 6, 25))
+		validate_calendar_frequencies("start date", "Biennial", None)
+		validate_calendar_frequencies("calendar months", "Yearly", None)
+
 	def test_get_date_period(self):
 		eval_date = date(2022, 11, 7)
 		initial_date = date(2022, 6, 25)
@@ -65,23 +105,6 @@ def test_get_date_period(self):
 		self.assertEqual(from_date, date(2022, 6, 25))
 		self.assertEqual(to_date, date(2025, 6, 24))
 
-	def test_get_calendar_period_unsupported_frequencies(self):
-		with self.assertRaises(frappe.ValidationError):
-			get_calendar_period(date(2022, 11, 7), Frequency.Biennial)
-
-		with self.assertRaises(frappe.ValidationError):
-			get_calendar_period(date(2022, 11, 7), Frequency.Triennial)
-
-	def test_validate_start_date_only_frequencies(self):
-		with self.assertRaises(frappe.ValidationError):
-			validate_start_date_only_frequencies("calendar months", "Biennial")
-
-		with self.assertRaises(frappe.ValidationError):
-			validate_start_date_only_frequencies("calendar months", "Triennial")
-
-		validate_start_date_only_frequencies("start date", "Biennial")
-		validate_start_date_only_frequencies("calendar months", "Yearly")
-
 	def test_get_from_and_to_date(self):
 		from_date, to_date = get_from_and_to_date(
 			frequency=Frequency.Monthly,
@@ -153,3 +176,23 @@ def test_get_from_and_to_date(self):
 		)
 		self.assertEqual(from_date, date(2022, 6, 25))
 		self.assertEqual(to_date, date(2025, 6, 24))
+
+		from_date, to_date = get_from_and_to_date(
+			frequency=Frequency.Biennial,
+			period_type=PeriodType.CalendarMonths,
+			billing_time=BillingTime.AtBeginningOfPeriod,
+			eval_date=date(2023, 6, 15),
+			start_date=date(2022, 6, 25),
+		)
+		self.assertEqual(from_date, date(2022, 1, 1))
+		self.assertEqual(to_date, date(2023, 12, 31))
+
+		from_date, to_date = get_from_and_to_date(
+			frequency=Frequency.Biennial,
+			period_type=PeriodType.CalendarMonths,
+			billing_time=BillingTime.AfterEndOfPeriod,
+			eval_date=date(2023, 12, 31),
+			start_date=date(2022, 6, 25),
+		)
+		self.assertEqual(from_date, date(2020, 1, 1))
+		self.assertEqual(to_date, date(2021, 12, 31))

From 881975ce935e45f86ff17259429fb870d62d46f9 Mon Sep 17 00:00:00 2001
From: HenningWendtland <156231187+HenningWendtland@users.noreply.github.com>
Date: Tue, 16 Jun 2026 11:48:28 +0200
Subject: [PATCH 4/5] chore: regenerate and update translation files

---
 simple_subscription/locale/de.po    | 25 +++++++++++++------------
 simple_subscription/locale/main.pot | 25 +++++++++++++------------
 2 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/simple_subscription/locale/de.po b/simple_subscription/locale/de.po
index df5a709..5872677 100644
--- a/simple_subscription/locale/de.po
+++ b/simple_subscription/locale/de.po
@@ -7,7 +7,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: Simple Subscription VERSION\n"
 "Report-Msgid-Bugs-To: hallo@alyf.de\n"
-"POT-Creation-Date: 2026-06-15 11:45+0053\n"
+"POT-Creation-Date: 2026-06-16 11:37+0053\n"
 "PO-Revision-Date: 2024-12-02 17:26+0053\n"
 "Last-Translator: hallo@alyf.de\n"
 "Language: de\n"
@@ -53,7 +53,7 @@ msgstr "Rechnungszeit"
 msgid "Company"
 msgstr "Unternehmen"
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js:53
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js:28
 msgid "Create current {0} invoice"
 msgstr "Aktuelle {0} Rechnung erstellen"
 
@@ -89,7 +89,7 @@ msgstr ""
 msgid "Disabled"
 msgstr ""
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:128
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:135
 msgid "Failed to create subscription invoice"
 msgstr "Fehler beim Erstellen der Abo-Rechnung"
 
@@ -98,10 +98,6 @@ msgstr "Fehler beim Erstellen der Abo-Rechnung"
 msgid "Frequency"
 msgstr "Frequenz"
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:196
-msgid "Frequency {0} is only supported when billing period is based on start date."
-msgstr "Die Frequenz {0} ist nur verfügbar, wenn die Abrechnungsperiode auf dem Startdatum basiert."
-
 #. Option for the 'Frequency' (Select) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Halfyearly"
@@ -133,15 +129,15 @@ msgstr ""
 msgid "Monthly"
 msgstr "Monatlich"
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:50
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:57
 msgid "Please amend Subscription {0} before creating a Sales Invoice."
 msgstr "Bitte ändern Sie das Abo {0} bevor Sie eine Rechnung erstellen."
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:44
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:51
 msgid "Please enable Subscription {0} before creating a Sales Invoice."
 msgstr "Bitte aktivieren Sie das Abo {0} bevor Sie eine Rechnung erstellen."
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:47
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:54
 msgid "Please submit Subscription {0} before creating a Sales Invoice."
 msgstr "Bitte buchen Sie das Abo {0} bevor Sie eine Rechnung erstellen."
 
@@ -155,7 +151,7 @@ msgstr ""
 msgid "Quarterly"
 msgstr "Vierteljährlich"
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:117
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:124
 msgid "Sales Invoice already exists for this period: {}"
 msgstr "Rechnung für diese Periode existiert bereits: {}"
 
@@ -186,7 +182,12 @@ msgstr "Vertrieb"
 #. Label of the start_date (Date) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Start Date"
-msgstr ""
+msgstr "Startdatum"
+
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:209
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:221
+msgid "Start Date is required for frequency {0}."
+msgstr "Startdatum ist für die Frequenz {0} erforderlich."
 
 #. Name of a role
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
diff --git a/simple_subscription/locale/main.pot b/simple_subscription/locale/main.pot
index d3eac1f..a8c2ac1 100644
--- a/simple_subscription/locale/main.pot
+++ b/simple_subscription/locale/main.pot
@@ -7,8 +7,8 @@ msgid ""
 msgstr ""
 "Project-Id-Version: Simple Subscription VERSION\n"
 "Report-Msgid-Bugs-To: hallo@alyf.de\n"
-"POT-Creation-Date: 2026-06-15 11:45+0053\n"
-"PO-Revision-Date: 2026-06-15 11:45+0053\n"
+"POT-Creation-Date: 2026-06-16 11:37+0053\n"
+"PO-Revision-Date: 2026-06-16 11:37+0053\n"
 "Last-Translator: hallo@alyf.de\n"
 "Language-Team: hallo@alyf.de\n"
 "MIME-Version: 1.0\n"
@@ -51,7 +51,7 @@ msgstr ""
 msgid "Company"
 msgstr ""
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js:53
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.js:28
 msgid "Create current {0} invoice"
 msgstr ""
 
@@ -87,7 +87,7 @@ msgstr ""
 msgid "Disabled"
 msgstr ""
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:128
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:135
 msgid "Failed to create subscription invoice"
 msgstr ""
 
@@ -96,10 +96,6 @@ msgstr ""
 msgid "Frequency"
 msgstr ""
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:196
-msgid "Frequency {0} is only supported when billing period is based on start date."
-msgstr ""
-
 #. Option for the 'Frequency' (Select) field in DocType 'Simple Subscription'
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "Halfyearly"
@@ -131,15 +127,15 @@ msgstr ""
 msgid "Monthly"
 msgstr ""
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:50
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:57
 msgid "Please amend Subscription {0} before creating a Sales Invoice."
 msgstr ""
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:44
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:51
 msgid "Please enable Subscription {0} before creating a Sales Invoice."
 msgstr ""
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:47
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:54
 msgid "Please submit Subscription {0} before creating a Sales Invoice."
 msgstr ""
 
@@ -153,7 +149,7 @@ msgstr ""
 msgid "Quarterly"
 msgstr ""
 
-#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:117
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:124
 msgid "Sales Invoice already exists for this period: {}"
 msgstr ""
 
@@ -186,6 +182,11 @@ msgstr ""
 msgid "Start Date"
 msgstr ""
 
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:209
+#: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py:221
+msgid "Start Date is required for frequency {0}."
+msgstr ""
+
 #. Name of a role
 #: simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json
 msgid "System Manager"

From 602c717fdc80bac83d2b3178d47da42d094030cc Mon Sep 17 00:00:00 2001
From: HenningWendtland <156231187+HenningWendtland@users.noreply.github.com>
Date: Wed, 17 Jun 2026 12:40:27 +0200
Subject: [PATCH 5/5] fix: pass only start_year and replace frappe.throw in
 get_calendar_period

---
 .../simple_subscription.py                    | 40 ++++++++++---------
 .../test_simple_subscription.py               | 18 ++++-----
 2 files changed, 30 insertions(+), 28 deletions(-)

diff --git a/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py b/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py
index db2fca8..8571c7f 100644
--- a/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py
+++ b/simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py
@@ -104,13 +104,18 @@ def get_price_list(self) -> str | None:
 @frappe.whitelist()
 def create_current_invoice(subscription_name: str, silent=False):
 	subscription = frappe.get_doc("Simple Subscription", subscription_name)
-	from_date, to_date = get_from_and_to_date(
-		frequency=Frequency[subscription.frequency],
-		eval_date=date.today(),
-		period_type=PeriodType(subscription.period_type),
-		billing_time=BillingTime(subscription.billing_time),
-		start_date=subscription.start_date,
-	)
+	try:
+		from_date, to_date = get_from_and_to_date(
+			frequency=Frequency[subscription.frequency],
+			eval_date=date.today(),
+			period_type=PeriodType(subscription.period_type),
+			billing_time=BillingTime(subscription.billing_time),
+			start_date=subscription.start_date,
+		)
+	except ValueError as e:
+		if not silent:
+			frappe.throw(str(e))
+		return
 
 	# check that start_date is not in the future
 	if subscription.start_date and subscription.start_date > from_date:
@@ -184,6 +189,8 @@ def get_from_and_to_date(
 	if not billing_time:
 		billing_time = BillingTime.AfterEndOfPeriod
 
+	start_year = start_date.year if start_date else None
+
 	if period_type == PeriodType.StartDate and billing_time == BillingTime.AtBeginningOfPeriod:
 		return get_date_period(eval_date, frequency, start_date)
 	elif period_type == PeriodType.StartDate and billing_time == BillingTime.AfterEndOfPeriod:
@@ -194,10 +201,10 @@ def get_from_and_to_date(
 			start_date,
 		)
 	elif period_type == PeriodType.CalendarMonths and billing_time == BillingTime.AtBeginningOfPeriod:
-		return get_calendar_period(eval_date, frequency, start_date)
+		return get_calendar_period(eval_date, frequency, start_year)
 	elif period_type == PeriodType.CalendarMonths and billing_time == BillingTime.AfterEndOfPeriod:
-		current_period_start, _ = get_calendar_period(eval_date, frequency, start_date)
-		return get_calendar_period(current_period_start - timedelta(days=1), frequency, start_date)
+		current_period_start, _ = get_calendar_period(eval_date, frequency, start_year)
+		return get_calendar_period(current_period_start - timedelta(days=1), frequency, start_year)
 
 
 def validate_calendar_frequencies(period_type: str, frequency: str, start_date: date | None) -> None:
@@ -213,19 +220,14 @@ def validate_calendar_frequencies(period_type: str, frequency: str, start_date:
 
 
 def get_calendar_period(
-	eval_date: date, frequency: Frequency, start_date: date | None = None
+	eval_date: date, frequency: Frequency, start_year: int | None = None
 ) -> tuple[date, date]:
 	"""Return the first and last day of the calendar period containing `eval_date`."""
-	if frequency in MULTI_YEAR_FREQUENCIES and not start_date:
-		frappe.throw(
-			_("Start Date is required for frequency {0}.").format(
-				_(frequency.name, context="Frequency of Subscription")
-			)
-		)
-
 	if frequency in MULTI_YEAR_FREQUENCIES:
+		if not start_year:
+			raise ValueError("start_year is required for multi-year frequencies")
 		years_span = frequency.value // 12
-		block_start_year = start_date.year + ((eval_date.year - start_date.year) // years_span) * years_span
+		block_start_year = start_year + ((eval_date.year - start_year) // years_span) * years_span
 		from_date = date(block_start_year, 1, 1)
 	else:
 		from_date = eval_date.replace(day=1, month=INVOICE_MONTH_MAP[frequency][eval_date.month - 1])
diff --git a/simple_subscription/simple_subscription/doctype/simple_subscription/test_simple_subscription.py b/simple_subscription/simple_subscription/doctype/simple_subscription/test_simple_subscription.py
index b48834e..efa1d60 100644
--- a/simple_subscription/simple_subscription/doctype/simple_subscription/test_simple_subscription.py
+++ b/simple_subscription/simple_subscription/doctype/simple_subscription/test_simple_subscription.py
@@ -37,33 +37,33 @@ def test_get_calendar_period(self):
 		self.assertEqual(from_date, date(2022, 1, 1))
 		self.assertEqual(to_date, date(2022, 12, 31))
 
-		start_date = date(2022, 6, 25)
+		start_year = date(2022, 6, 25).year
 
-		from_date, to_date = get_calendar_period(date(2022, 11, 7), Frequency.Biennial, start_date)
+		from_date, to_date = get_calendar_period(date(2022, 11, 7), Frequency.Biennial, start_year)
 		self.assertEqual(from_date, date(2022, 1, 1))
 		self.assertEqual(to_date, date(2023, 12, 31))
 
-		from_date, to_date = get_calendar_period(date(2023, 6, 15), Frequency.Biennial, start_date)
+		from_date, to_date = get_calendar_period(date(2023, 6, 15), Frequency.Biennial, start_year)
 		self.assertEqual(from_date, date(2022, 1, 1))
 		self.assertEqual(to_date, date(2023, 12, 31))
 
-		from_date, to_date = get_calendar_period(date(2024, 3, 1), Frequency.Biennial, start_date)
+		from_date, to_date = get_calendar_period(date(2024, 3, 1), Frequency.Biennial, start_year)
 		self.assertEqual(from_date, date(2024, 1, 1))
 		self.assertEqual(to_date, date(2025, 12, 31))
 
-		from_date, to_date = get_calendar_period(date(2024, 6, 15), Frequency.Triennial, start_date)
+		from_date, to_date = get_calendar_period(date(2024, 6, 15), Frequency.Triennial, start_year)
 		self.assertEqual(from_date, date(2022, 1, 1))
 		self.assertEqual(to_date, date(2024, 12, 31))
 
-		from_date, to_date = get_calendar_period(date(2025, 1, 1), Frequency.Triennial, start_date)
+		from_date, to_date = get_calendar_period(date(2025, 1, 1), Frequency.Triennial, start_year)
 		self.assertEqual(from_date, date(2025, 1, 1))
 		self.assertEqual(to_date, date(2027, 12, 31))
 
-	def test_get_calendar_period_multi_year_requires_start_date(self):
-		with self.assertRaises(frappe.ValidationError):
+	def test_get_calendar_period_multi_year_requires_start_year(self):
+		with self.assertRaises(ValueError):
 			get_calendar_period(date(2022, 11, 7), Frequency.Biennial)
 
-		with self.assertRaises(frappe.ValidationError):
+		with self.assertRaises(ValueError):
 			get_calendar_period(date(2022, 11, 7), Frequency.Triennial)
 
 	def test_validate_calendar_frequencies(self):