diff --git a/api/app/services/anaf_service.py b/api/app/services/anaf_service.py
index 5bc24c3..127a6fc 100644
--- a/api/app/services/anaf_service.py
+++ b/api/app/services/anaf_service.py
@@ -22,10 +22,61 @@ def strip_ro_prefix(cod_fiscal: str) -> str:
 
 
 def validate_cui(bare_cui: str) -> bool:
-    """Validate bare CUI: digits only, length 1-13."""
+    """Validate bare CUI: digits only, length 2-10."""
     if not bare_cui:
         return False
-    return bare_cui.isdigit() and 1 <= len(bare_cui) <= 13
+    return bare_cui.isdigit() and 2 <= len(bare_cui) <= 10
+
+
+# Cheia de testare CUI Romania (9 ponderi, aliniate la dreapta cu cifrele fara cifra de control)
+_CUI_KEY = [7, 5, 3, 2, 1, 7, 5, 3, 2]
+
+
+def validate_cui_checksum(bare_cui: str) -> bool:
+    """Validate CUI check digit using the Romanian algorithm.
+
+    Algorithm: pad to 9 digits (without check digit), multiply by key 753217532,
+    sum products, (sum * 10) % 11 → if 10 then 0, else result == check digit.
+    """
+    if not validate_cui(bare_cui):
+        return False
+    digits = [int(d) for d in bare_cui]
+    check_digit = digits[-1]
+    body = digits[:-1]
+    # Pad left with zeros to 9 positions
+    padded = [0] * (9 - len(body)) + body
+    total = sum(d * k for d, k in zip(padded, _CUI_KEY))
+    result = (total * 10) % 11
+    if result == 10:
+        result = 0
+    return result == check_digit
+
+
+def sanitize_cui(raw_cf: str) -> tuple[str, str | None]:
+    """Sanitize and validate CUI. Returns (clean_cui, warning_or_none).
+
+    Steps: strip RO prefix, fix OCR typos (O→0), validate checksum.
+    If sanitized version passes checksum but original didn't, returns the fixed CUI.
+    If neither passes, returns original with warning.
+    """
+    bare = strip_ro_prefix(raw_cf)
+    if not bare:
+        return bare, None
+
+    if validate_cui(bare) and validate_cui_checksum(bare):
+        return bare, None
+
+    # Try without OCR fix (raw, just stripped)
+    raw_bare = re.sub(r'^RO\s*', '', raw_cf.strip().upper())
+    if raw_bare != bare and validate_cui(raw_bare) and validate_cui_checksum(raw_bare):
+        return raw_bare, None
+
+    # Sanitized version passes format but not checksum
+    if validate_cui(bare):
+        return bare, f"CUI {bare} nu trece verificarea cifrei de control"
+
+    # Not even valid format
+    return bare, f"CUI {raw_cf!r} contine caractere invalide dupa sanitizare: {bare!r}"
 
 
 async def check_vat_status_batch(cui_list: list[str], date: str = None) -> dict[str, dict]:
diff --git a/api/app/services/sync_service.py b/api/app/services/sync_service.py
index 0e558e5..fb8c736 100644
--- a/api/app/services/sync_service.py
+++ b/api/app/services/sync_service.py
@@ -659,7 +659,7 @@ async def run_sync(id_pol: int = None, id_sectie: int = None, run_id: str = None
                 is_ro = (order.billing.country or "").strip().lower() == "romania"
                 if order.billing.is_company and order.billing.company_code and is_ro:
                     raw_cf = import_service.clean_web_text(order.billing.company_code) or ""
-                    bare = anaf_service.strip_ro_prefix(raw_cf)
+                    bare, _ = anaf_service.sanitize_cui(raw_cf)
                     if anaf_service.validate_cui(bare):
                         company_cuis.add(bare)
 
@@ -702,7 +702,9 @@ async def run_sync(id_pol: int = None, id_sectie: int = None, run_id: str = None
                 raw_cf = ""
                 if order.billing.is_company and order.billing.company_code:
                     raw_cf = import_service.clean_web_text(order.billing.company_code) or ""
-                    bare_cui = anaf_service.strip_ro_prefix(raw_cf)
+                    bare_cui, cui_warning = anaf_service.sanitize_cui(raw_cf)
+                    if cui_warning:
+                        _log_line(run_id, f"#{order.number} WARN: {cui_warning}")
                     anaf_data_for_order = cached_results.get(bare_cui)
                     if anaf_data_for_order and anaf_data_for_order.get("scpTVA") is not None:
                         correct_cf = anaf_service.determine_correct_cod_fiscal(bare_cui, anaf_data_for_order["scpTVA"])