SALF202 - Self Assessment Tax Returns: introduction
Source: gov.uk (2025-11-07)


Self Assessment (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’. When a notice to file, or a return containing the notice to file has been given, the filing date for a paper tax return is 31 October following the end of the year of assessment, and, the filing date for electronic returns is 31 January, unless the notice to file, or the tax return containing the notice to file a return is given after 31 July. In this case the return must be delivered within 3 months beginning with the date of the notice to file or 31 January if this is later, and the return is filed electronically.

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

A filing date of at least 3 months is given to allow a reasonable amount of time for the tax return to be completed. Where a taxpayer wants HMRC to calculate the tax and a notice to file, or a tax return containing the notice to file a return is given after 31 August following the end of the tax year, the tax return must be delivered to HMRC within 2 months beginning with the day on which the notice is given. This is 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 penalties when a notice to file or a tax return containing the notice to file is given and the return is made and delivered to HMRC after the filing date.

Voluntary Returns

Voluntary returns are returns received from customers or agents where HMRC have not given a notice to the customer to make the return. HMRC’s long standing policy of treating them as statutory returns has been put beyond doubt as from 12 February 2019 new law was introduced which has retrospective and prospective effect. All voluntary returns should now be treated as having been made in response to a notice to file which was given to the person on the same date the return was received by HMRC.

The filing date for a voluntary paper return is 31 October following the end of the tax year, unless the return is received after 31 July following the end of the tax year, in which case the filing date is 3 months after the date it was received.

The filing date for electronic returns is 31 January following the end of the tax year, unless the return is received after 31 October following the end of the tax year in which case the filing date is 3 months after the date it was received

As a voluntary return will always be received on the same date a notice is treated as given, it can never be late. A late filing penalty will therefore not apply to voluntary returns.

HMRC procedures are focused on the processing of tax returns and on enquiries into the accuracy of those returns. Returns may be amended by HMRC to correct any obvious errors or omissions within 9 months beginning with the date the return was delivered to HMRC. Customers or agents may also be contacted by telephone in order to clarify certain entries on the return. This approach will generally 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.