Company Number format

My understanding was that English company numbers are 8 digits long and start with a 0 (zero)?

I was trialling the streaming API and found some 8 digit company numbers beginning with 1 which failed my validation. I checked and they are registered companies in England.

What have I missed? What is the current document reference?



Standard company numbers are sequential and hit 8 digits a few years ago (2016 or 2017 I think). So they haven’t had the leading zero since then. A company formed today will be 12 followed by another six digits (ie

There are also a few different two character prefix/six number variants you may need to account for (OC, LP, FC, SC, NI, RC possibly more? They’re all I know of)

Ash beat me to it but for what it is worth:

All company numbers are 8 units in length but may have alpha prefixes (e.g. SC or NI) or suffices (usually linked with ab IP or RS prefix. Very early number start with multiple leading zeros; the latest numbers start with1. Leading zeros will also appear in early numbers that have an alpha prefix (e.g SC00NNNN). To be sure you have the right entity you ALWAYS need the full eight unit set! that is unique!

Also might be worth noting that the 8 characters with leading zeroes format as standard is relatively recent (well the last couple of decades anyway). At a guess it’s related to the gradual transition to digital storage of this information. Some older programs and a lot of older paperwork will only store or render the significant digits. This has been an issue for us in the past when integrating with some older data sources, not so much recently though and but shouldn’t really affect anything API related.

Great. So any 8 digit numeric number is valid, we just happen to be at 12XXXXXX ?

Anything that comes from an API will reference an 8 digit company number but paper (pdf image) may contain numbers with stripped zero’s.

I am on top of the 2 char 6 numbers. variants I think, but Frank’s comment " Leading zeros will also appear after early numbers that have an alpha prefix" is a new one on me. I thought anything that started with an alpha was going to be 8 digit. Does that mean I can have say a 6 digit SC number ??

What i was expressing rather badly was that an alpha prefix may be followed by one or more “leading” zeros to pack out to a total of 8 units so SC00NNNN or SC0NNNNN; have amended the original post to make clearer

I found this reference, which appears to date from either 2011 or May 2012: Companies House Uniform Resource Identifiers (URI) Customer Guide.