Finnish IBAN Validator

Finnish IBANs follow a tightly specified 18-character structure governed by ISO 13616 and verified with the ISO 7064 MOD-97-10 checksum algorithm. Whether you are wiring a SEPA payment to a Finnish supplier, onboarding a freelancer based in Helsinki, or reconciling a Finnish payroll run, a single transposed digit will cause the payment to be rejected or bounce — usually with a 1-3 business day delay and a return-charge fee. This validator catches every structural error before you submit anything.

Paste or type any IBAN beginning with FI and the tool instantly checks three things in parallel: the exact length (18 characters — one of the shorter IBANs in the SEPA zone), the BBAN composition (all digits, no letters), and the ISO 7064 MOD-97-10 checksum. It also extracts the bank code — the first three digits of the 14-digit BBAN — and maps it to the issuing Finnish institution using the publicly documented Finnish Banking Association registry. You get the formatted IBAN (grouped in blocks of four, e.g. FI21 1234 5600 0007 85) with a one-click copy button. Everything runs locally — no number is ever sent to a server.

Finland’s banking landscape is dominated by a small number of groups. OP Financial Group (Osuuspankit) is the largest cooperative banking network in the Nordics and uses bank codes 400-500. Nordea Bank Finland holds codes 003-019. Aktia Bank, Alandsbanken, and S-Pankki each occupy tightly bounded code ranges, as do specialist providers like Holvi (899) and the co-operative POP Pankki savings banks (715-725). Knowing which institution issued an IBAN is useful both for fraud-checks and for routing queries to the right customer service team.

How it works

A Finnish IBAN is built from four parts joined end to end:

1. Country code — the fixed two-letter code FI
2. Check digits — two digits chosen so that, when the whole IBAN is rearranged and divided by 97, the remainder equals exactly 1
3. Bank and branch field — six digits where the first three identify the bank and the remaining three historically identify the branch (positions 5-10)
4. Account and domestic check — seven account digits plus one domestic check digit (positions 11-18)

The MOD-97 algorithm works like this: move the first four characters (FI + check digits) to the end of the string, then replace every letter with its numeric equivalent (F becomes 15, I becomes 18). The resulting all-numeric string — 22 digits for a Finnish IBAN — is divided by 97. The IBAN is valid if and only if the remainder is 1. Because the number is too large for direct JavaScript integer arithmetic, the tool computes the modulus progressively, folding one digit at a time so the running value never exceeds a safe integer.

Worked example

Suppose you receive the Finnish IBAN FI21 1234 5600 0007 85 from a contractor.

1. Strip spaces: FI2112345600000785
2. Length check: 18 characters. Pass.
3. BBAN digits-only check: characters 5-18 are 12345600000785. All digits. Pass.
4. Rearrange: move FI21 to the end: 12345600000785FI21
5. Expand letters: F=15, I=18: 123456000007851518 21 Full numeric string: 1234560000078515 1821
6. Compute mod 97 progressively over the full string: remainder is 1. Pass.
7. Bank code 123 maps to Citibank Finland.

All three checks pass, so the IBAN is structurally valid. The formatted output FI21 1234 5600 0007 85 is ready to copy.

Every calculation runs locally. Nothing is uploaded, transmitted, or logged.