IBAN Validator mod-97 & ISO 13616
The IBAN (International Bank Account Number) validator instantly checks any IBAN for correctness using the mod-97 checksum algorithm defined in ISO 13616. It verifies the country code, check digits, and the BBAN (Basic Bank Account Number) structure according to each country's specific format rules.
About the IBAN Validator
The IBAN (International Bank Account Number) validator instantly checks any IBAN for correctness using the mod-97 checksum algorithm defined in ISO 13616. It verifies the country code, check digits, and the BBAN (Basic Bank Account Number) structure according to each country's specific format rules.
All 36 SEPA countries are supported. No data is ever sent to a server — validation happens entirely in your browser, making it safe to use with real account numbers.
The IBAN was introduced to standardize cross-border bank account identification. Each country defines its own IBAN length and BBAN structure: a Belgian IBAN has 16 characters (BE + 2 check digits + 12-digit BBAN), a French IBAN has 27 characters, and a German IBAN has 22 characters. The mod-97 checksum catches over 99% of transcription errors, including single character mistakes and most transpositions.
This tool is particularly useful for finance teams preparing SEPA payment files: validating IBANs before including them in a pain.001 or pain.008 file prevents rejection by your bank. A single invalid IBAN in a batch of hundreds of payments can cause the entire file to be rejected, delaying all payments. Pre-checking each IBAN takes seconds and eliminates this risk.
What is an IBAN?
An IBAN (International Bank Account Number) is a standardized international numbering system for identifying bank accounts across national borders. It consists of a two-letter country code, two check digits calculated using the mod-97 algorithm, and a country-specific Basic Bank Account Number (BBAN). IBANs reduce errors in international payments and are mandatory for SEPA transactions.
Key Takeaways
- IBANs use a mod-97 checksum to detect transcription errors before payment submission
- Each country has a fixed IBAN length (e.g., DE=22, FR=27, BE=16, NL=18, GB=22)
- The IBAN contains the bank code and account number — it fully identifies a bank account
- ValidateFin validates IBAN format, length, checksum, and country code instantly
- Always validate IBANs before including them in SEPA payment files to prevent rejection
IBAN format by country
| Country | IBAN length | Example |
|---|---|---|
| Belgium (BE) | 16 | BE68 5390 0754 7034 |
| France (FR) | 27 | FR76 3000 6000 0112 3456 7890 189 |
| Germany (DE) | 22 | DE89 3704 0044 0532 0130 00 |
| Netherlands (NL) | 18 | NL91 ABNA 0417 1643 00 |
| Spain (ES) | 24 | ES91 2100 0418 4502 0005 1332 |
| Italy (IT) | 27 | IT60 X054 2811 1010 0000 0123 456 |
IBANs displayed with spaces for readability. In payment files, IBANs must be sent without spaces.
Frequently Asked Questions
How does IBAN validation work?
The tool performs a mod-97 checksum algorithm on the full IBAN, then verifies the country code, check digits, and BBAN format according to the country-specific rules. For a deeper dive, read our IBAN validation guide.
Which countries are supported?
All 36 SEPA countries are supported, including EU member states, UK, Norway, Switzerland, and other participating countries.
Does the validator check BIC codes as well?
The IBAN validator focuses on IBAN verification. For full payment file validation including BIC, use the SEPA Validator.
Is this tool free to use?
Yes, completely free with no registration required. IBAN validation runs entirely in your browser.
What is the mod-97 checksum algorithm?
The mod-97 algorithm is defined in ISO 13616. To validate an IBAN: move the first 4 characters to the end, replace each letter with its numeric equivalent (A=10, B=11... Z=35), then compute the number modulo 97. A valid IBAN always yields a remainder of 1. This method detects all single-digit errors and most transposition errors.
What is the BBAN and how does it vary by country?
The BBAN (Basic Bank Account Number) is the national account identifier within the IBAN. Its format varies by country: for example, a French IBAN has a 10-digit bank/branch code followed by an 11-digit account number and 2 check digits, while a German IBAN uses an 8-digit bank code and a 10-digit account number. The validator checks the BBAN length and character type (numeric or alphanumeric) for all 36 supported countries.
Can an IBAN pass the checksum but still be invalid for a real bank?
Yes. The mod-97 checksum verifies the mathematical integrity of the IBAN, but it cannot confirm that the account actually exists at a bank or that the bank code corresponds to a real institution. For payment processing, always verify IBANs against a live banking directory or through your bank's pre-validation service.
What is the maximum IBAN length?
IBANs vary in length from 15 characters (Norway) to 34 characters (Malta). The total length includes the 2-letter country code, 2 check digits, and the country-specific BBAN. The validator automatically checks that the IBAN length matches the expected length for the detected country.
Why does my IBAN fail validation even though my bank provided it?
A few common reasons: the IBAN may have been copied with spaces or formatting characters (remove all spaces before validating), a digit may have been transposed during manual entry, or the IBAN was provided without the country prefix. Paste the full IBAN including the country code (e.g. BE71 0961 2345 6769) and remove all spaces. Once corrected, you can validate your full payment file with the SEPA Validator.
Is it safe to validate real IBAN numbers with this tool?
Yes. IBAN validation runs entirely in your browser — no data is sent to any server. Your IBANs are not stored, logged, or transmitted. This makes it safe to validate real customer or supplier account numbers.