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HMRC internal manual

Self Assessment: the legal framework

Self Assessment Tax Returns: introduction

SA gives the responsibility for creating the correct legal tax charge to the taxpayer.

Under SA a tax return is a return of all the information needed to calculate the taxpayer’s total taxable income (from all sources) and any chargeable gains, for the period covered by the return. The calculation of the tax due may then be carried out by either:

  • the taxpayer, whose calculation of the tax due - a ‘self assessment’ - forms part of the tax return, or
  • HMRC. All such ‘HMRC calculations’ are treated as if they are self assessments.

There are fixed dates for completed tax returns to be delivered to HMRC - often called the ‘filing date’. The filing date for a paper tax return is 31 October following the end of the year of assessment. The filing date for electronic returns is 31 January. If the tax return or notice to file is issued after 31 July then the return must be submitted by 3 months after the date of issue or 31 January if later and the return is filed electronically.

Where the taxpayer wants HMRC to calculate the tax, the ‘self assessment’, the tax return must be received by 31 October following the tax year, if the return or notice to file was issued before 31 July.

A different filing date applies where a tax return or notice to file is issued late, to allow a reasonable amount of time for the tax return to be completed. In HMRC calculation cases earlier filing dates apply, to allow HMRC to calculate the tax due and notify the taxpayer accordingly.

A legal charge to tax is created by the receipt of a completed self assessment, or, in HMRC calculation cases, by the issue of the notice of the tax payable. The due date for payment of that tax is 31 January following the tax year to which the tax return relates. This charge arises automatically, without the need for additional action by HMRC.

There are sanctions to deter late filing of tax returns, including automatic penalties.

HMRC procedures are focused on the processing of tax returns and on enquiries into the accuracy of those returns. At the processing stage returns may be amended by HMRC to correct any obvious errors or omissions. Customers or agents may also be contacted by telephone in order to clarify certain entries on the return. This approach will be taken to ensure that the return is successfully processed at the first attempt and will only be undertaken where the query is minor. Any major doubts about the accuracy of the return or technical issues will be dealt with through the enquiry procedures.