# Check-Digit and Checksum Validation

Normalize an identifier, select its specified checksum path, and verify format before accepting it.

> Canonical page: https://elysiatools.com/en/hubs/check-digit-checksum-validation

- **Keywords:** check digit, checksum validation, Luhn, Mod 11

## Frequently asked questions

### Does a valid checksum prove the identifier exists?

No. It proves only internal consistency under the implemented rules.

### When should separators be removed?

Only when the specification treats them as display characters.

### When is Luhn insufficient?

When length, prefixes, alphabet, weights, or additional identifier rules apply.