Verify existing IBAN check digits.
Initialising algorithm engine for IBAN Checksum Validator...
How IBAN Checksum Validator Works?
The IBAN Checksum Validator works by moving the first 4 characters of the IBAN to the end, converting letters to numbers, and confirming that the remainder modulo 97 equals 1.
- 1Remove spaces and convert the IBAN to upper case.
- 2Check the length against the country's fixed IBAN length.
- 3Move the country code and check digits to the end.
- 4Replace letters with 2-digit numbers (A = 10 … Z = 35).
- 5Mark the IBAN valid when the number mod 97 = 1.
IBAN Checksum Validator Formula
The IBAN validation formula is num(BBAN + CC + check digits) mod 97 = 1.
valid ⇔ num(IBAN[4:] ‖ IBAN[0:4]) mod 97 = 1
IBAN[4:]is everything after the check digits.IBAN[0:4]is country code plus check digits.
Rearranged = WEST12345698765432GB82 Numeric = 3214282912345698765432161182 mod 97 = 1 Result = valid
IBAN Checksum Validator Conversion Table
The IBAN validation table shows valid IBANs next to versions with a single typing error.
| IBAN | Remainder mod 97 | Result | Error introduced |
|---|---|---|---|
| GB82 WEST 1234 5698 7654 32 | 1 | Valid | None |
| GB28 WEST 1234 5698 7654 32 | 44 | Invalid | Check digits swapped (82 → 28) |
| DE89 3704 0044 0532 0130 00 | 1 | Valid | None |
| DE89 3704 0044 0532 0310 00 | 31 | Invalid | Adjacent digits swapped (13 → 31) |
| NL91 ABNA 0417 1643 00 | 1 | Valid | None |
| PK36 SCBL 0000 0011 2345 6702 | 1 | Valid | None |
| FR14 2004 1010 0505 0001 3M02 606 | 1 | Valid | None |
| FR14 2004 1010 0505 0001 3N02 606 | 6 | Invalid | Letter changed (M → N) |
What is IBAN Checksum Validator?
An IBAN Checksum Validator is a tool that verifies the 2 check digits of an existing International Bank Account Number. A valid checksum confirms the IBAN was typed correctly but does not prove the account exists.
Banks reject payments with invalid IBANs before processing, so a validator catches the error before a payment fails.
What are the uses of IBAN Checksum Validator?
There are 4 main uses of the IBAN Checksum Validator, including invoice checks, vendor master data, and payment form validation.
- Invoice checks: Accounts payable teams verify supplier IBANs on invoices.
- Vendor master data: Finance teams clean IBANs in ERP vendor records.
- Payment forms: Websites check IBANs before submission.
- Fraud screening: Analysts flag IBANs altered after a typing check.