iXBRL

iXBRL (Inline eXtensible Business Reporting Language) is the format HMRC requires for the accounts and tax computations sent with a Company Tax Return, produced with commercial software¹. The document reads like ordinary accounts, but each figure also carries a machine-readable tag.

Why it matters

You don’t tag anything yourself: filing software produces it. From April 2028, Companies House will also require every company to file its accounts in iXBRL through commercial software, and its web and paper filing for accounts will close².

See HMRC’s free filing service has closed for what to look for in software.