The annual accounts and tax computation attached to a CT600 corporation tax return must in iXBRL format.
An iXBRL file has the same format as a page on a web site and the accounts or computation it contains can be viewed in any web browser simply by opening the file. In addition, much of the data is specially tagged so that it can also be machine read.
The accounts and computations in the VT workbooks in VT Final Accounts are pre-tagged and iXBRL files can be generated from them at the touch of a button.
To generate an iXBRL file, select VT XBRL>Generate iXBRL File from the Add-ins menu in Excel.
VT Final Accounts can also be used to self-tag any set of accounts or computation in any Excel workbook. For most small companies, custom accounts and computations can be tagged very quickly using a special dialog laid out in the form of a set accounts/computation. No technical knowledge is required.
The iXBRL accounts and tax computation files generated by VT can be attached to third party tax packages for filing a corporation tax return.
iXBRL accounts can also be submitted to Companies House using VT Filer.
Many users will not need knowledge of iXBRL, or what needs to be tagged, however if you need to know a bit more about tagging, then you should refer to HMRC's document: XBRL tagging: when, what and how to tag.