Sequence number
A sequence number is a consecutive integer used to identify items in a series. They appear in many places, such as serial numbers on parts, in case management, or in databases as a surrogate key (a primary key) to identify each entry uniquely.
In Norway, sequence numbers have been used as placeholders in land registration when a company number or national identity number isn’t known.
In Norwegian elections, sequence numbers help prevent counting the same vote twice or detecting duplicate ballots.
An example is the snr number used by Statistics Norway since 1970. It uniquely identifies a person, even if their social security number changes, and can be linked to both social security numbers to keep a single, stable identifier.
Sometimes people distinguish a sequence number from a serial number. For example, a locomotive may have a code like “Re 465 003-2,” which shows how serial numbers can look different from simple sequence numbers.
This page was last edited on 2 February 2026, at 17:58 (CET).