National Bank Account Checksum Tool

How National Bank Account Checksum Tool Works?

The National Bank Account Checksum Tool works by applying the domestic check digit rule of the selected country to the account number before any IBAN conversion. Each country uses its own weights, modulus, and field layout.

1. 1Select the country.
2. 2Split the account number into the fields the country defines (bank, branch, account, key).
3. 3Apply the country's weights and modulus to the defined fields.
4. 4Compare the computed check digits with the supplied ones.
5. 5Report a match, a mismatch, or the missing digits.

National Bank Account Checksum Tool Formula

The national account check formula is Check = f_country(account fields), where f is a weighted modulus 10, 11, or 97 rule.

Belgium:     check = (first 10 digits) mod 97, 0 → 97
Netherlands: Σ dᵢ × (10 − i) mod 11 = 0  (legacy 9-digit test)
Norway:      weights 5,4,3,2,7,6,5,4,3,2 → 11 − (S mod 11)
Spain:       2 control digits, weights 1,2,4,8,5,10,9,7,3,6
France:      key = 97 − ((89·bank + 15·branch + 3·account) mod 97)

• dᵢ is the i-th account digit.
• S is the country-specific weighted total.

Weighted sum = 147
Check = 11 − (147 mod 11) = 7
Account = 8601 11 17947

National Bank Account Checksum Tool Conversion Table

The national account conversion table lists 6 countries with their domestic rule and a computed sample.

What is National Bank Account Checksum Tool?

A National Bank Account Checksum Tool is a tool that checks domestic bank account numbers with the country-specific rules that existed before the IBAN. The domestic checks still sit inside the BBAN portion of each IBAN.

Germany alone uses more than 100 check digit methods (Prüfzifferberechnungsmethoden), assigned per bank code by the Deutsche Bundesbank.

What are the uses of National Bank Account Checksum Tool?

There are 3 main uses of the National Bank Account Checksum Tool, including domestic payments, IBAN conversion, and payroll imports.

• Domestic payments: Billers verify local account numbers before submitting direct debits.
• IBAN conversion: Banks confirm the BBAN is valid before wrapping it in an IBAN.
• Payroll imports: HR teams validate employee account numbers in payroll files.