diff --git a/.github/find_missing_sources.py b/.github/find_missing_sources.py
new file mode 100644
index 0000000..fd395f3
--- /dev/null
+++ b/.github/find_missing_sources.py
@@ -0,0 +1,143 @@
+#!/usr/bin/env python3
+"""
+find_missing_source.py
+
+Place this file in:
+  root_folder/.github/find_missing_source.py
+
+It will automatically scan:
+  root_folder/Data
+
+and write output next to the script (in .github/) by default.
+"""
+
+from __future__ import annotations
+
+import argparse
+import os
+from pathlib import Path
+from typing import Optional, Tuple
+
+import pandas as pd
+
+
+def detect_source_column(columns) -> Optional[str]:
+    """Return the actual column name whose stripped lowercase equals 'source'."""
+    for c in columns:
+        if str(c).strip().lower() == "source":
+            return c
+    return None
+
+
+def read_csv_robust(path: Path) -> Tuple[Optional[pd.DataFrame], Optional[str]]:
+    """Read CSV with delimiter sniffing and tolerant parsing."""
+    try:
+        df = pd.read_csv(
+            path,
+            sep=None,               # sniff delimiter
+            engine="python",        # required for sep=None
+            dtype=str,              # keep as strings
+            keep_default_na=True,
+            on_bad_lines="skip",
+            encoding_errors="replace",
+        )
+        return df, None
+    except Exception as e:
+        return None, f"{type(e).__name__}: {e}"
+
+
+def is_missing_source(series: pd.Series) -> pd.Series:
+    """True if value is NaN or only whitespace after stripping."""
+    s = series.astype("string")
+    return s.isna() | (s.str.strip() == "")
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser()
+    ap.add_argument(
+        "--out",
+        type=str,
+        default="missing_sources.xlsx",
+        help="Output file name (.csv or .xlsx). Default: missing_sources.xlsx",
+    )
+    ap.add_argument(
+        "--include-errors",
+        action="store_true",
+        help="Also write a *_errors.csv listing unreadable CSVs and reasons.",
+    )
+    args = ap.parse_args()
+
+    # Script is in root_folder/.github/
+    script_dir = Path(__file__).resolve().parent              # root_folder/.github
+    root_folder = script_dir.parent                           # root_folder
+    data_dir = root_folder / "Data"                           # root_folder/Data
+
+    if not data_dir.exists() or not data_dir.is_dir():
+        raise SystemExit(f'Expected folder not found: "{data_dir}"')
+
+    out_path = (script_dir / args.out).resolve()
+
+    missing_rows = []
+    errors = []
+
+    for dirpath, _, filenames in os.walk(data_dir):
+        for fn in filenames:
+            if not fn.lower().endswith(".csv"):
+                continue
+
+            csv_path = Path(dirpath) / fn
+            df, err = read_csv_robust(csv_path)
+            if df is None:
+                errors.append({"file": str(csv_path), "error": err})
+                continue
+
+            source_col = detect_source_column(df.columns)
+            if source_col is None:
+                # No source column; skip silently (or record as error if you want)
+                continue
+
+            mask = is_missing_source(df[source_col])
+            if not mask.any():
+                continue
+
+            hit = df.loc[mask].copy()
+
+            # Add traceability columns
+            # Store path relative to root_folder for cleaner output
+            rel_path = csv_path.relative_to(root_folder)
+            hit.insert(0, "__file__", str(rel_path))
+
+            # Row number in original file: +2 to account for header being row 1
+            hit.insert(1, "__row__", (hit.index.to_series() + 2).astype(int))
+
+            missing_rows.append(hit)
+
+    if missing_rows:
+        result = pd.concat(missing_rows, ignore_index=True)
+    else:
+        result = pd.DataFrame(columns=["__file__", "__row__"])
+
+    # Write main output
+    if out_path.suffix.lower() == ".xlsx":
+        with pd.ExcelWriter(out_path, engine="openpyxl") as writer:
+            result.to_excel(writer, index=False, sheet_name="missing_source")
+    else:
+        result.to_csv(out_path, index=False, encoding="utf-8")
+
+    # Optionally write errors
+    if args.include_errors:
+        err_path = out_path.with_name(out_path.stem + "_errors.csv")
+        pd.DataFrame(errors).to_csv(err_path, index=False, encoding="utf-8")
+
+    print(f"Script location: {script_dir}")
+    print(f"Scanning folder:  {data_dir}")
+    print(f"Missing rows:     {len(result)}")
+    print(f"Wrote output:     {out_path}")
+    if args.include_errors:
+        print(f"Wrote errors:     {err_path}")
+
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/.github/workflows/missing-source-check.yml b/.github/workflows/missing-source-check.yml
new file mode 100644
index 0000000..ac964e2
--- /dev/null
+++ b/.github/workflows/missing-source-check.yml
@@ -0,0 +1,90 @@
+name: Missing Source Check
+
+on:
+  pull_request:
+    paths:
+      - "**/*.csv"   # only run when CSVs change
+
+permissions:
+  contents: read
+  pull-requests: write   # needed for PR comments
+  issues: write          # comments are issued via the Issues API for PRs
+
+jobs:
+  missing-source:
+    runs-on: ubuntu-latest
+
+    outputs:
+      missing_count: ${{ steps.count.outputs.missing_count }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install pandas openpyxl
+
+      - name: Run missing-source scan
+        run: |
+          python .github/find_missing_sources.py --out missing_sources.csv
+
+      - name: Count missing rows
+        id: count
+        shell: bash
+        run: |
+          # Count data rows in CSV (minus header). If file is empty/nonexistent, count = 0.
+          if [ -f ".github/missing_sources.csv" ]; then
+            lines=$(wc -l < ".github/missing_sources.csv" | tr -d ' ')
+            if [ "$lines" -gt 0 ]; then
+              missing_count=$((lines - 1))
+            else
+              missing_count=0
+            fi
+          else
+            missing_count=0
+          fi
+
+          echo "missing_count=$missing_count" >> "$GITHUB_OUTPUT"
+          echo "Missing rows: $missing_count" >> "$GITHUB_STEP_SUMMARY"
+
+      - name: Upload report artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: missing-sources-report
+          path: .github/missing_sources.csv
+          if-no-files-found: warn
+
+      # Optional: Fail the check if missing rows exist (uncomment if you want to block merges)
+      # - name: Fail if missing rows found
+      #   if: ${{ steps.count.outputs.missing_count != '0' }}
+      #   run: |
+      #     echo "Found missing source rows: ${{ steps.count.outputs.missing_count }}"
+      #     exit 1
+
+      - name: Comment on PR (skips forks)
+        if: ${{ github.event.pull_request.head.repo.fork == false }}
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const missing = Number("${{ steps.count.outputs.missing_count }}");
+            const runUrl = `${context.serverUrl}/${context.repo.owner}/${context.repo.repo}/actions/runs/${context.runId}`;
+
+            const body =
+              `🧾 **Missing Source Check**\n\n` +
+              `Missing rows: **${missing}**\n\n` +
+              `Download the artifact (**missing-sources-report**) from the workflow run:\n` +
+              `${runUrl}`;
+
+            await github.rest.issues.createComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+              body
+            });
diff --git a/Data/Parameters/Par_AnnualMinNewCapacity/Europe_EnVis_Green/Par_AnnualMinNewCapacity.csv b/Data/Parameters/Par_AnnualMinNewCapacity/Europe_EnVis_Green/Par_AnnualMinNewCapacity.csv
index 4ed0dc8..359ab67 100644
--- a/Data/Parameters/Par_AnnualMinNewCapacity/Europe_EnVis_Green/Par_AnnualMinNewCapacity.csv
+++ b/Data/Parameters/Par_AnnualMinNewCapacity/Europe_EnVis_Green/Par_AnnualMinNewCapacity.csv
@@ -17,3 +17,4 @@ UK,P_Nuclear,2040,1.631,,GW,Partner Feedback Man0EUvRE - Sandrine Charousset,03.
 UK,P_Nuclear,2045,1.632,,GW,Partner Feedback Man0EUvRE - Sandrine Charousset,03.06.2025,Nikita Moskalenko <nim@wip.tu-berlin.de>
 TR,P_Nuclear,2025,1.2,,GW,Partner Feedback Man0EUvRE - Sandrine Charousset,03.06.2025,Nikita Moskalenko <nim@wip.tu-berlin.de>
 TR,P_Nuclear,2030,3.6,,GW,Partner Feedback Man0EUvRE - Sandrine Charousset,03.06.2025,Nikita Moskalenko <nim@wip.tu-berlin.de>
+TR,TEST,All,0.1,,GW,,,Test