iXBRL (inline eXtensible Business Reporting Language) is a file format that tags each figure in a set of accounts or a tax computation so that software can read it, while the document still looks normal to a person. HMRC and Companies House require it for software filing.
How it works
An iXBRL file is a web page with hidden labels. Each figure and key fact is tagged with a code from a published list called a taxonomy, saying what it is (turnover, tangible fixed assets, the company number), which period it belongs to and what currency it is in. People read the page as usual; HMRC and Companies House read the tags.
Where it is required
- HMRC: the accounts and the tax computation sent with a CT600 must both be in iXBRL.
- Companies House: accounts filed with software are in iXBRL. From 1 April 2028 all accounts must be filed this way.
In Tax Optimiser
You do not tag anything yourself. Tax Optimiser tags the accounts and computation as it builds them and checks them before filing.
Read more: Reviewing your documents, iXBRL package accounts and Preparing for April 2028.