The following supplementary pages are supported:
HMRC's software also includes accounts and computations templates. If you use these, you don't need to worry about sending this information in the right format. This will be done for you automatically.
Alternatively you can attach your own accounts and computations. For most companies the accounts file you attach must be in Inline eXtensible Business Reporting Language (iXBRL). Unincorporated organisations can submit their accounts in either iXBRL format or as a PDF. Computations must always be in iXBRL format.
You can also attach other supporting documents that are needed as part of your return, for example claims or elections, reports or statements. These attachments must be in PDF format.
Please note: The maximum combined file size for attachments when using the HMRC downloadable software is 5MB.