Business ID Validator
Check an identifier’s checksum before a payment goes out — catching a mistyped digit here is considerably cheaper than catching it afterwards.
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How it works
Most business identifiers carry a check digit derived from the rest of the string, specifically so a single mistyped character can be detected. The algorithms are published standards, which means the verification can happen entirely in your browser with no lookup.
What this proves and what it does not are worth separating. A valid checksum means the identifier is correctly formed — it does not mean the account exists, the business is registered or the counterparty is who they claim. It catches typos, not fraud.
IBAN: rearrange, convert letters to digits, check mod 97 = 1 · Luhn: doubled-digit sum mod 10 = 0
- IBAN — international bank account number — mod-97 check across the whole string
- GSTIN — 15-character Indian tax identifier with a base-36 weighted check digit
- ABN — 11-digit Australian business number, weighted mod 89
- Luhn — the mod-10 scheme used by payment cards and many national IDs
Worked example
Validating the IBAN GB82 WEST 1234 5698 7654 32
Inputs
Results
Change any single character and the mod-97 check fails — which is exactly what the check digits exist to do.
Frequently asked questions
Does a valid checksum mean the account exists?
No. It means the identifier is correctly formed and free of typos. Confirming that an account or registration actually exists requires checking with the bank or the relevant registry.
Why does my valid-looking IBAN fail?
Most often a transposed pair of characters, a letter O entered as a zero, or a country-specific length mismatch. The mod-97 check catches all single-character errors and almost all transpositions, which is why it is worth running.
Is my identifier sent anywhere?
No. Every algorithm here is implemented in the page and runs in your browser. Nothing you type leaves the device, which matters given these are exactly the strings you would not want logged.
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