W-IdNr
Validator
Check whether a German Wirtschafts-Identifikationsnummer (W-IdNr) is correctly formatted and passes the official ISO/IEC 7064 Mod 11,10 checksum — entirely in your browser.
About W-IdNr Validation (Germany)
The Wirtschafts-Identifikationsnummer (W-IdNr) is Germany's unified business identifier, enacted under § 139c of the German Fiscal Code (AO) and issued by the Federal Central Tax Office (BZSt).
The format starts with the prefix "DE" followed by 9 digits (with a check digit computed by ISO 7064 Mod 11,10) and a 5-digit differentiator suffix (Unterscheidungsmerkmal) preceded by a hyphen, e.g. DE123456789-00001.
Anatomy & Structure of W-IdNr
| Position | Field | Length | Meaning & Rule | Example |
|---|---|---|---|---|
| 1 and 2 | Country (ISO) | 2 letters | Sovereign code for Germany in ISO 3166-1 alpha-2 standard | DE |
| 3 to 10 | Base Number | 8 digits | Main numerical business identifier assigned by the BZSt | 12345678 |
| 11 | Prüfziffer (Check Digit) | 1 digit | Check digit computed according to ISO/IEC 7064, Mod 11, 10 | 9 |
| 12 to 16 | Unterscheidungsmerkmal | 5 digits | Differentiator suffix for establishment/branch (00001 for main headquarters) | 00001 |
Validation Algorithm of W-IdNr (ISO/IEC 7064, Mod 11, 10)
| Step | Description |
|---|---|
| 1. Isolate the base and suffix | Isolate the DE prefix and the 5-digit differentiator suffix (separated by an optional hyphen). |
| 2. Initialize the product | Initialize the product variable P = 10 for the first 8 digits. |
| 3. Sum and update per digit | For each digit, calculate S = (digit + P) % 10 (if 0, reset to 10) and P = (S × 2) % 11. |
| 4. Compute the check digit | Calculate check digit C = 11 − P (if 10, the check digit is 0; otherwise equal to C). |
| 5. Verify digit and suffix range | The 9th digit must match C, and the suffix must be between 00001 and 99999. |
Frequently Asked Questions & Technical Specifications
What is the difference between USt-IdNr and W-IdNr?
The USt-IdNr is specifically for EU cross-border VAT transactions and has existed for decades. The W-IdNr is a newer, broader business identifier (introduced under § 139c AO) meant to eventually serve as a single reference number across all German authorities and registers — it also encodes individual business units and branches via its 5-digit suffix, which the USt-IdNr does not.
Are the generated numbers real or official?
No. This validator only checks whether a number satisfies the ISO/IEC 7064 Mod 11,10 checksum and suffix range used by the W-IdNr format — it does not look up any real business registration. A result of "valid" means the number is mathematically well-formed, not that it belongs to a real company.