SEDOL Validator & Check-Digit Calculator
Validate SEDOLs (Stock Exchange Daily Official List codes) and compute their check digit. A SEDOL is a 7-character alphanumeric code — a 6-character national security identifier and a single trailing check digit — that identifies UK and international securities. It uses digits 0–9 and the 21 consonant letters (the vowels A E I O U are never used), with a weighted-sum check-digit algorithm distinct from Luhn. Everything runs locally in your browser.
Validate a SEDOL
Compute check digit
SEDOL structure: positions 1–6 are the alphanumeric NSIN, position 7 is the check digit. Allowed characters are 0–9 and the consonant letters B C D F G H J K L M N P Q R S T V W X Y Z — vowels are reserved to avoid confusion with digits. Each character has a numeric value: digits → themselves (0–9); a letter → its 1-based place among the consonants plus 9, giving B=10, C=11, … Z=30. The check digit is computed by multiplying the six NSIN values by the fixed weights [1, 3, 1, 7, 3, 9], summing, then taking (10 − sum mod 10) mod 10. Validation recomputes that digit and compares it to the 7th character. New-style SEDOLs (international securities) start with B; older UK ones are purely numeric. SEDOLs are case-insensitive on input (uppercased here). Pairs with the ISIN and IBAN validators. Everything runs locally — nothing leaves your browser.