A new proposal that will see company tax returns being completed and returned online using XBRL instead of in PDF format could be 'costly and problematic' says the Chartered Institute of Taxation. HM Revenue & Customs is currently consulting on the legislation to be implemented for April 2011, although the department has advised companies to switch over before it becomes mandatory. The CIOT has made a call for a deferral or an embargo on penalties for the first year.