A regex to check UK Company numbers - ie the reference assigned to companies in the UK via Companies House

UK Company Number regex

/^((AC|ZC|FC|GE|LP|OC|SE|SA|SZ|SF|GS|SL|SO|SC|ES|NA|NZ|NF|GN|NL|NC|R0|NI|EN|\d{2}|SG|FE)\d{5}(\d|C|R))|((RS|SO)\d{3}(\d{3}|\d{2}[WSRCZF]|\d(FI|RS|SA|IP|US|EN|AS)|CUS))|((NI|SL)\d{5}[\dA])|(OC(([\dP]{5}[CWERTB])|([\dP]{4}(OC|CU))))$/

Hi,

The published guide for URI is here:
https://assets.publishing.service.gov.uk/media/5d08c0f340f0b6094a379078/uniformResourceIdentifiersCustomerGuide.pdf

I gave the @mrbrianevans version a go.

I downloaded the companies house public database http://download.companieshouse.gov.uk/en_output.html
Its 2.6Gb or so extracted, so created a new file containing only the company numbers (50MB) and ran the regex against it.

Got only 1 failure: "RS007853Z"

Added the exception to the regex, this is passing with the complete dataset as per Feb 2025:

^(((AC|CE|CS|FC|FE|GE|GS|IC|LP|NC|NF|NI|NL|NO|NP|OC|OE|PC|R0|RC|SA|SC|SE|SF|SG|SI|SL|SO|SR|SZ|ZC|\\d{2})\\d{6})|((IP|SP|RS)[A-Z\\d]{6})|(SL\\d{5}[\\dA])|(RS007853Z))$