Understanding SEDOL: UK Securities Identification

What is SEDOL?

SEDOL (Stock Exchange Daily Official List) is a seven-character alphanumeric identifier assigned to securities traded on the London Stock Exchange and other UK exchanges. It’s used to identify listed and unlisted securities across asset classes (stocks, unit trusts, investment trusts, insurance-linked securities, etc.) and is recognized internationally.

Structure and character rules

• Total characters: 7
• First six: alphanumeric (digits 0–9 and letters B–Z; vowels are not used)
• Seventh: check digit (0–9)
• Before 26 January 2004, SEDOLs were numeric only. After that date letters were introduced; post-2004 SEDOLs typically begin with a letter.
• Letters map to numeric values for checksum calculation: value = 9 + alphabetical position.
• Example: C = 9 + 3 = 12

Check digit and weights

The seventh character is chosen so that the weighted sum of all seven characters is a multiple of 10. The position weights are:

Position: 1 2 3 4 5 6 7
Weight: 1 3 1 7 3 9 1

To compute the weighted sum:
1. Convert letters to their numeric values (as above).
2. Multiply each character’s numeric value by its position weight.
3. Add the results. The total must be divisible by 10.

Example: HSBC (SEDOL 0540528)

Characters: 0 5 4 0 5 2 8
Weighted sum:
0×1 + 5×3 + 4×1 + 0×7 + 5×3 + 2×9 + 8×1 = 0 + 15 + 4 + 0 + 15 + 18 + 8 = 60
60 is a multiple of 10, so the check digit (8) is correct.

When are new SEDOLs issued?

New SEDOLs may be issued for events such as:
– Corporate headquarters changes
– Mergers or takeovers
– New ISINs
– Company name changes
– Share reclassifications

Why SEDOL matters

• Provides a unique, standardized identifier that reduces trade failures and settlement errors.
• Enables efficient cross-border trading and clear asset tracking.
• Maintained by the London Stock Exchange in the SEDOL Masterfile.

SEDOL vs. CUSIP

• SEDOL: 7 characters, primarily used in the UK and Ireland (recognized internationally).
• CUSIP: 9 characters, primarily used in the U.S. and Canada; structured as 6-character issuer code, 2-character issue code, 1 check digit.
  They serve the same purpose (unique security IDs) but are regionally focused and not interchangeable; some securities may have both.

Quick facts

• Stands for Stock Exchange Daily Official List.
• Assigned and maintained by the London Stock Exchange.
• Used primarily in the UK and Ireland but recognized globally.
• Consists of six identifier characters plus one check digit (seven characters total).

Key takeaway

SEDOL is a concise, standardized identifier that helps ensure accurate identification, processing, and settlement of securities traded on UK exchanges and beyond.