Valid Company Number format

We have a set of company numbers provided by user in free text format with no size limit and format validation. We try to validate the Company information provided by user by searching the company number using Companies House API. Many of them won’t return any result.

The peak load can be as high as 30~40 calls / second. We want to reduce this by filtering out invalid Company Numbers before we hit companieshouse.gov.uk . Can someone point me to the website containing information about what is valid? And is there future possibility of extending the length of company number from current 8 ?

@zeliang

The attached provides information on the format of current company numbers

Thanks

@mfairhurst