What does the mod-97 checksum actually check?

It verifies the IBAN's two check digits are mathematically consistent with the rest of the number per ISO 7064, which catches mistyped or invalid IBANs. It does not confirm the account itself exists or is active.

How is the country code used in validation?

The first two letters of the IBAN identify the issuing country, which also determines the IBAN's expected total length for that country, both are checked as part of validating the number.

IBAN Validator

Check if an IBAN passes the mod-97 checksum.

How this is calculated

Mod-97 checksum (ISO 7064): rearranged, letter-converted IBAN must be ≡ 1 (mod 97)

Assumptions used in this calculation

Format check only: This only checks the checksum format, it does not verify the account exists or is active.

About this calculator

The IBAN validator checks whether an International Bank Account Number passes the ISO 7064 mod-97 checksum and identifies its country code.

Worked example

GB29 NWBK 6016 1331 9268 19

Result: Valid IBAN

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Frequently asked questions

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IBAN Validator

About this calculator

Frequently asked questions

What does the mod-97 checksum actually check?

How is the country code used in validation?

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