Slovakia’s IBAN is 24 characters with an all-numeric BBAN, pattern ^[0-9]{20}$, mirroring the Czech format field for field. What distinguishes the Slovak page of the IBAN registry is not structure but currency: Slovakia has been a euro country since 2009.
Field layout
The official registry example SK31 1200 0000 1987 4263 7541 (a published SWIFT test value, not a live account) breaks down as:
SK31- country code and IBAN check digits1200- 4-digit bank code assigned by the National Bank of Slovakia000019- the 6-digit account prefix, zero-padded (domestically written as 19 before a hyphen)8742637541- the 10-digit base account number
Domestic Slovak notation, like Czech, historically wrote this as prefix-number/bankcode, with the bank code trailing after a slash. Building the IBAN moves the bank code to the front and pads both numeric parts, so hand-conversion of old records needs care.
Inherited checksum rules
The Czechoslovak legacy includes weighted modulo-11 self-checks on both the prefix and the base account number. A Slovak IBAN from a real bank therefore passes three independent tests: the two national modulo-11 checks and the IBAN’s own MOD-97 checksum. Validators that implement only the ISO layer will accept some strings no Slovak bank could ever have issued, so country-aware checking adds real value here.
Euro-native SEPA member
Because Slovakia is in the eurozone, SK IBANs need no currency caveats within SEPA: euro credit transfers and direct debits to Slovak accounts settle without conversion, and Slovak consumers use the same IBAN for everything from salaries to utility direct debits. Cross-border payments from neighbouring Czechia, still on the koruna, are a routine source of confusion between the visually similar CZ and SK formats; the country code and check digits will catch a swapped prefix, since the same BBAN yields different check digits under each country code.
Formal validity, as always, is not proof of existence. A perfectly checked SK IBAN can point at a closed or unissued account, which is why EU Verification of Payee name matching runs before your bank releases the funds.