Updated 2026 · 6 min read
An IBAN, or International Bank Account Number, is a standardised format for identifying bank accounts across international borders. If you've ever sent money abroad and been asked for a long string of letters and numbers instead of a simple account number, that was almost certainly an IBAN. Instead of every country using its own unique account-numbering system with no common structure, an IBAN wraps a bank's domestic account details in a consistent, machine-readable format that any bank in any of the 77 participating countries can validate and process automatically.
The IBAN standard was developed by the European Committee for Banking Standards in the late 1990s, initially to simplify cross-border payments within Europe as the euro was being introduced. It was formalised as ISO 13616 and later adopted far beyond Europe — across the Middle East, parts of the Caribbean, and other regions — though notably not by the United States, Canada, Australia, or most of Asia, which continue to use their own domestic identifiers like routing numbers or IFSC codes.
Every IBAN has three parts. First, a 2-letter ISO country code (GB for the United Kingdom, DE for Germany, AE for the UAE). Second, 2 check digits used to validate the whole number via a mod-97 checksum. Third, the Basic Bank Account Number (BBAN) — the country's own domestic account format, which usually includes a bank code, sometimes a branch code, and the account number itself. Total length varies by country: Norway's IBANs are the shortest at 15 characters, Malta's are the longest at 31.
Take the UK example GB29 NWBK 6016 1331 9268 19. GB is the country code, 29 is the check digits, and the remaining 18 characters are the BBAN: NWBK is the bank code (NatWest), 601613 is the 6-digit sort code, and 31926819 is the 8-digit account number. Every IBAN country structures its BBAN slightly differently, but the country code and check digits always come first.
The errors people run into most often are: transposing two digits when typing an IBAN by hand, dropping a character so the length no longer matches the country's requirement, pasting an IBAN with hidden spaces or line breaks that don't get stripped before submission, and confusing an IBAN with a SWIFT/BIC code — these are different codes with different purposes, and international transfers to IBAN countries typically need both.
Banqcheq's free IBAN validator checks all of this in under a second: it confirms the country code is valid, checks the length matches that country's standard, runs the official ISO 7064 mod-97 checksum, and looks up the bank name where recognised. There's no sign-up and no limit on how many times you can check — just paste the IBAN and click Validate.
Whether you're a finance team double-checking a new vendor's bank details or an individual sending money abroad for the first time, catching an IBAN error before you submit a payment saves days of delay and, in some cases, a lost transfer entirely.
Before IBAN, a bank receiving an international payment had to interpret an unfamiliar domestic account format from another country by hand, or via bespoke bilateral agreements between specific banks — slow, error-prone, and expensive to maintain at scale. IBAN's self-describing structure (country code first, checksum second) means any receiving bank's system can validate an incoming payment instruction automatically, without needing prior knowledge of that specific country's domestic format. That's the entire reason the checksum exists: it lets a computer catch a transcription error algorithmically, in milliseconds, rather than a human discovering the mistake days later when a payment fails to arrive.
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