Two checks for Belgian IBANs
Every IBAN has two check digits after the country code, verified with the ISO 13616 mod-97 rule — that catches almost all typos. A Belgian IBAN
(BE + 14 characters) also contains the old 12-digit account number, which has its own check: the first 10 digits mod 97 must equal the last two.
Both are checked here.
Bank and BIC
The first three digits of the Belgian account number are the bank identification code, assigned by the National Bank of Belgium (NBB). The tool looks it up in the official NBB list (version shown above) to show the bank and its BIC. A BIC isn't required for SEPA payments between EU accounts, but some systems still ask for it. Note that an account may have moved banks after a merger; the code shows the institution the range belongs to.
Old account numbers
Numbers written 123-4567890-12 are converted to IBAN automatically.