iXBRL is the machine-readable accounts format HMRC already requires and Companies House filing moves to in 2028. Here is what it means for you.
iXBRL is the format company accounts have to be filed in electronically. HMRC has required it for years, and from April 2028 Companies House filing moves to it too. You do not usually create iXBRL by hand, but it helps to understand what it is and why it is behind the 2028 change. This guide explains it in plain terms.
What iXBRL is
iXBRL stands for inline eXtensible Business Reporting Language. It is a way of preparing a document that is readable by a person and by a computer at the same time. The accounts look like a normal report, but hidden tags label each figure, so software can read the numbers automatically.
Why it exists
Tagging the figures lets HMRC and Companies House process accounts automatically and check them against other data, instead of reading every set by hand. It is the reason electronic filing can be instant, and the reason the format has to be exact.
Where it is already required
If you file a Company Tax Return, you already use iXBRL. HMRC requires the CT600 and its accounts in iXBRL, produced either by its free online service or by commercial software. Most directors never see the tags because the software adds them.
Why 2028 makes it matter for Companies House
Today you can file accounts to Companies House on a free web form that does the formatting for you. From April 2028 that web form closes and accounts must be filed using software in iXBRL. In other words, the format HMRC has always required becomes the only way to file with Companies House too.
What it means for you
You will not write iXBRL yourself. What you need is software that produces it. The risk for small and dormant companies is being pushed toward paid, complex accounting packages just to file simple accounts. We are building a free tool that generates compliant iXBRL accounts for small, micro and dormant companies, so the 2028 change does not mean a new bill.