Identify schemes with check characters.
Initialising algorithm engine for Check Digit Support Lookup...
How Check Digit Support Lookup Works?
The Check Digit Support Lookup shows whether a scheme uses check characters. It searches a reference list and reports the number of check characters and the algorithm used.
- 1Type the identifier name or abbreviation.
- 2Select the matching scheme from the list.
- 3Read whether the scheme has a check character.
- 4Read the check length and the algorithm.
- 5Open the matching calculator from the result.
Check Digit Support Lookup Formula
The lookup rule is Result = registry[scheme] → (has check, length, algorithm).
registry: scheme → { hasCheck: bool, length: n, algorithm: name }registryis the scheme reference list.
Scheme found: US Social Security Number Has check digit: No Validation: format rules only (area, group, serial)
Check Digit Support Lookup Conversion Table
The Check Digit Support Lookup table lists 12 common identifiers and whether each carries a check character.
| Identifier | Has check character | Check length | Algorithm |
|---|---|---|---|
| EAN-13 / UPC-A | Yes | 1 digit | GS1 Mod 10 |
| ISBN-10 | Yes | 1 character (0–9, X) | Mod 11 |
| IBAN | Yes | 2 digits | ISO 7064 MOD 97-10 |
| Payment card | Yes | 1 digit | Luhn |
| US Social Security Number | No | — | None |
| UK National Insurance number | No | — | None |
| Aadhaar | Yes | 1 digit | Verhoeff |
| Passport number (MRZ) | Yes | 1 digit | ICAO 7-3-1 |
| US EIN | No | — | None |
| UK sort code | No (account check via modulus tables) | — | Vocalink modulus checking |
| ISSN | Yes | 1 character (0–9, X) | Mod 11 |
| Phone number (E.164) | No | — | None |
What is Check Digit Support Lookup?
A Check Digit Support Lookup is a reference tool that tells whether a given identifier scheme includes a check character. Well-known numbers such as US Social Security Numbers and phone numbers carry none.
Knowing that a scheme has no check digit prevents teams from writing validation that rejects valid numbers.
What are the uses of Check Digit Support Lookup?
There are 3 main uses of the Check Digit Support Lookup, including validation design, compliance reviews, and teaching.
- Validation design: Developers learn which fields can be checksum-validated.
- Compliance reviews: Auditors confirm that controls match the identifier type.
- Teaching: Trainers show which identifiers protect against typos.