Simply put, over the next 3 years, all self-employed people will need to start doing accounting in HMRC-approved software that will send quarterly updates to the tax system.  Although self-employed people have always kept records and accounts, people have been allowed to submit simplified accounts to HMRC for their tax calculation.  No more.    For many, this is a frustrating and overwhelming development.    You can read more about it here on the Gov website.