Update invoices.adoc

Author: AyeshaFirdausTG

modules/savanna/modules/administration/pages/billing/invoices.adoc

@@ -22,6 +22,34 @@ image::invoice_tab_.png[]
 
 . To export a specific invoice as a `.pdf` select the btn:[PDF] button under btn:[Export As].
 
+== Invoice status
+
+Each invoice status indicates the stage of an invoice in the billing lifecycle.
+
+=== In Billing Period
+
+The invoice period is ongoing and charges are still accumulating.
+
+image::In_billing_period.png[]
+
+=== In Grace Period
+
+The billing period has ended, but the system will automatically attempt payment after the grace period.
+
+image::In_grace_period.png[]
+
+=== Processing
+
+Invoice amount is being finalized and is not ready for payment.
+
+image::processing_.png[]
+
+=== No Payment Needed
+
+The invoice does not require payment (e.g., zero amount or covered by credits).
+
+image::no_payment_needed1.png[]
+
 == Next Steps
 
 Next, learn about other billing topics on the xref:savanna:administration:billing/index.adoc[] page or check out the xref:resources:index.adoc[] section.