🧮 SEDOL Check Digit System

SEDOL check digits use a weighted algorithm where each position has a specific multiplier (1,3,1,7,3,9,1). The sum of products is divided by 10, and the remainder subtracted from 10 gives the check digit. For Vodafone's SEDOL BH4HKS3, the calculation validates the final '3'. This system helps prevent errors in UK security identification and trading systems.