diff --git a/.github/workflows/domain-tables.yml b/.github/workflows/domain-tables.yml
index 16cc581..52dec78 100644
--- a/.github/workflows/domain-tables.yml
+++ b/.github/workflows/domain-tables.yml
@@ -7,6 +7,7 @@ on:
   pull_request:
     paths:
       - "tools/generate_domain_tables.py"
+      - "tools/audit_nt009_sources.py"
       - "tools/tests/test_generate_domain_tables.py"
       - "resources/domains/**"
       - ".github/workflows/domain-tables.yml"
diff --git a/tools/audit_nt009_sources.py b/tools/audit_nt009_sources.py
new file mode 100644
index 0000000..42c4499
--- /dev/null
+++ b/tools/audit_nt009_sources.py
@@ -0,0 +1,106 @@
+#!/usr/bin/env python3
+# SPDX-FileCopyrightText: 2026 LibreCode coop and contributors
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+"""Audit the exact NT009 XLSX inputs before changing offline tax domains.
+
+Run manually; never fetch external data from application runtime.
+The hashes are independent download observations recorded on 2026-10-05,
+not a published governmental checksum. Reconfirm against the official URLs.
+"""
+
+from __future__ import annotations
+
+import argparse
+import hashlib
+import json
+import re
+import tempfile
+import time
+import urllib.request
+from pathlib import Path
+
+from generate_domain_tables import Workbook
+
+SOURCES = {
+    "annex_vi": (
+        "https://www.gov.br/nfse/pt-br/biblioteca/documentacao-tecnica/rtc/"
+        "anexovi-leiautesrn_rtc_ibscbs-v1-04-01-nt009.xlsx",
+        "103a150dd6f56ec8edcaa3a453b59a1b0e096d7cd5025d7bd06a387f141ddf39",
+    ),
+    "annex_vii": (
+        "https://www.gov.br/nfse/pt-br/biblioteca/documentacao-tecnica/rtc/"
+        "anexovii-indop_ibscbs_v1-03-00-nt009.xlsx",
+        "95f30a44ee94adeea57fb92f3a0337b1e62fdc106f393e73894087889be9e5aa",
+    ),
+}
+
+
+def retrieve(url: str, destination: Path) -> bytes:
+    request = urllib.request.Request(
+        url, headers={"User-Agent": "LibreCodeCoop/nfse-php normative source audit"}
+    )
+    for attempt in range(4):
+        try:
+            with urllib.request.urlopen(request, timeout=45) as response:
+                payload = response.read()
+            destination.write_bytes(payload)
+            return payload
+        except (OSError, TimeoutError):
+            if attempt == 3:
+                raise
+            time.sleep(2 ** attempt)
+    raise RuntimeError("unreachable")
+
+
+def inspect_annex(name: str, path: Path, dump: bool) -> None:
+    with Workbook(path) as book:
+        print(f"{name}: sheets = {list(book.sheet_targets)}", flush=True)
+        if not dump:
+            return
+        for sheet in book.sheet_targets:
+            if name == "annex_vi" and "LEIAUTE DPS" not in sheet:
+                continue
+            rows = book.rows(sheet)
+            for number, cells in enumerate(rows, 1):
+                joined = " ".join(cells.values())
+                if name == "annex_vii":
+                    if not any(re.fullmatch(r"[0-9]{6}", re.sub(r"\D", "", val)) for val in cells.values()):
+                        if number > 12:
+                            continue
+                elif not any(marker in joined for marker in (
+                    "IBSCBS", "indDest", "finNFSe", "tpNFSeDebito",
+                    "tpNFSeCredito", "gPgtoVinc", "regApIBSCBSSN",
+                    "CST", "cClassTrib",
+                )):
+                    continue
+                print(f"{name}:{sheet}:{number}: {json.dumps(cells, ensure_ascii=False)}", flush=True)
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--inspect", action="store_true", help="Print source rows for manual normative review")
+    parser.add_argument("--output-dir", type=Path, help="Keep exact verified XLSX files here")
+    args = parser.parse_args()
+
+    def audit(destination: Path) -> None:
+        for name, (url, expected) in SOURCES.items():
+            path = destination / f"{name}.xlsx"
+            payload = retrieve(url, path)
+            actual = hashlib.sha256(payload).hexdigest()
+            print(f"{name}: {url} sha256={actual} bytes={len(payload)}", flush=True)
+            if actual != expected:
+                raise ValueError(f"{name}: source checksum differs from recorded observation {expected}")
+            inspect_annex(name, path, args.inspect)
+
+    if args.output_dir:
+        args.output_dir.mkdir(parents=True, exist_ok=True)
+        audit(args.output_dir)
+    else:
+        with tempfile.TemporaryDirectory() as temporary:
+            audit(Path(temporary))
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())