From 1 April 2011 all tax returns for companies and the accompanying accounts must be submitted online to HMRC using the special iXBRL programming language. You may receive a penalty if you submit a paper corporate tax return, or paper or PDF copies of company accounts to HMRC after that date.

HMRC have provided some free software that small companies with simple tax affairs can use to submit their tax return and accounts using the iXBRL standard, but it is quite difficult and time-consuming to use. We can submit your company’s tax return and accounts for you using commercial iXBRL software.

 iXBRL guide for UK businesses

http://www.hmrc.gov.uk/ct/ct-online/file-return/xbrl-guide.pdf