Austria keeps its IBAN simple: 20 characters, all numeric after the prefix, with the BBAN matching ^[0-9]{16}$. It is the same length as Kazakhstan’s and Kosovo’s IBANs but two characters shorter than neighbouring Germany’s.
Field by field
The official registry example AT61 1904 3002 3457 3201 (a SWIFT registry test value, not a real account) decomposes as:
AT61- country code and MOD-97 check digits19043- the 5-digit Bankleitzahl (BLZ)00234573201- the 11-digit Kontonummer, zero-padded on the left
The Austrian BLZ landscape
Austria’s 5-digit Bankleitzahl is administered by the central bank, and its first digit loosely signals the banking sector: savings banks, Raiffeisen cooperatives, Volksbanken and joint-stock banks each cluster in recognisable ranges. This matters in practice because Austria has an unusually dense network of small cooperative banks that merge regularly, retiring BLZ codes as they go. An IBAN that validated last year may reference a bank code that has since been absorbed - the payment usually still routes, but statements and records can show a successor institution.
Unlike Hungary or Belgium, the Austrian BBAN embeds no domestic check digit. Error detection rests entirely on the IBAN’s two ISO 7064 check digits, which reliably catch single-digit errors and transpositions but, like any checksum, cannot detect a wrong-but-well-formed number.
Domestic format and SEPA
Before SEPA, Austrians quoted BLZ and Kontonummer as two fields; the IBAN concatenates them without reordering, so converting old records is mechanical as long as the account number is padded to 11 digits correctly. Austria has been in SEPA from the beginning, and AT IBANs are fully usable for euro credit transfers and direct debits across the area.
As everywhere, formal validity is a floor, not a ceiling: it tells you the string could be an account, not that it is one. Verification of Payee name matching is the mechanism that actually protects against misdirected or fraudulent transfers. If you need test data, generate a structurally valid sample with the tool on this page instead of guessing digits.