Netherlands RSIN Validator (Elfproef)
Validate Dutch RSIN corporate tax numbers using the official 11-proof with negative final weight.
About the Dutch RSIN Number
The RSIN is the central corporate tax and identification number for legal entities (BV, NV, foundations, cooperatives) in the Netherlands.
Administered jointly by the KVK and the Belastingdienst, it links tax filings with the commercial register.
Anatomy & Structure of Dutch RSIN
The Dutch RSIN consists strictly of 9 numeric digits:
| Position | Field | Length | Meaning & Rule | Example |
|---|---|---|---|---|
| 1 to 8 | Base Number | 8 digits | Corporate sequential number issued by KVK | 12345678 |
| 9 | Check Digit | 1 digit | Security checksum verified by Elfproef | 2 |
Official Elfproef Algorithm for Legal Entities
Validation rule under the Dutch Commercial Register Act 2007:
Sum = Σ(d[i] * W[i]) [W = 9, 8, 7, 6, 5, 4, 3, 2, -1]; Sum > 0 && Sum mod 11 == 0
- 1. Extract all 9 numeric digits of the RSIN.
- 2. Multiply the first 8 digits by weights [9, 8, 7, 6, 5, 4, 3, 2].
- 3. Subtract the 9th digit multiplied by 1.
- 4. Confirm that the total sum is strictly greater than zero and divisible by 11.