Source:  HMRC

From April 2024, if you are self-employed or in a trading partnership, you have to report your profits on a tax year basis.    

Although businesses remain free to choose their accounting date and can prepare accounts to any date in the year, if they do not do so to a period between 31 March and 5 April they will need to apportion profits from 2 accounting periods to the tax year.    

If you do not already do so, for the tax year 2023 to 2024 you will need to declare your profits from the end of the previous accounting period in 2022 to 2023 up to 5 April 2024. Any additional profit, after overlap relief, will be transition profit. By default, this transition profit is spread equally over the next 5 years including 2023 to 2024.  

If you applied to HMRC to request your overlap relief figure on or before the filing deadline of 31 January 2025 using our overlap relief tool  but did not receive a response and have still not filed your return, you have until 28 February 2025 to file it with a provisional figure — or final figure if known. By doing so, you will not incur a late filing penalty, although interest will still accrue from 1 February 2025 on outstanding amounts of tax. You should then amend your return once the final figure is known. Tax can be paid without filing. Amounts paid will reduce any interest charged.  

Many businesses may find it easier to prepare accounts to 31 March or 5 April from 2024 onwards. This may make completing the tax return simpler as there will be no need to use 2 sets of accounts to complete each tax return. Accounting periods ending on 31 March will be treated as equivalent to those ending on 5 April for all businesses, including property businesses.  

Further guidance on how to amend Self Assessment tax returns is available.  

Further guidance to get help with basis period reform is available.