iXBRL stands for inline eXtensible Business Reporting Language.

It is an electronic filing format – a computer language used in the electronic filing of company accounts.

All tax returns filed in iXBRL are marked, tagged, read and understood by HMRC computers. Since it keeps the content and layout of all documents passed through it the same, all iXBRL tax returns will look exactly the same as any paper copies you file.

HMRC has stated that the use of iXBRL is compulsory for all accounting periods ending 31 March 2010 onward.