Should you really push to file your Self Assessment tax return by the 31st January 2026?

If you are one of the 5 million taxpayers who is yet to file your 2024/25 tax return, 23 days may not be enough to meet the deadline. When I have a client in this position, now is the time to walk through options and identify the next steps.

Do you need to make any elections by 31st January 2026 ?

If you are eligible to claim overseas workdays relief and have received your employment income into a qualifying overseas back account, ie a "Special Mixed Fund", you are required to nominate the account by 31st January 2026. This is typically done by including the details of the qualifying account in the additional information section of your tax return but if you are not in a position to file your tax return by 31st January 2026, you can send a letter to HMRC with details of the qualifying bank account you need to nominate.

Are you waiting for confirmation of sources of income?

If you need to declare a substantial amount of untaxed income but are still waiting for confirmation of the amounts to report, you could estimate the income income and the tax that will be due to HMRC, to help you decide whether to make an estimated payment to HMRC by 31st January 2026, to avoid late interest and penalties.

Are you waiting for a non-UK tax return to be finalised to enable you claim tax relief for the overseas taxes ?

It is common practice to estimate the tax relief that is due and file a tax return with a note specifying that the relief claim is an estimate and an amended tax return will follow once the overseas taxes are confirmed.

Do you need to submit an amended 2023/24 tax return?

The deadline to file an amended 2023/24 tax return online is 31st January 2026. If you have not yet done so, check to see whether the 2023/24 tax return you filed with HMRC includes estimates, eg foreign taxes.

Do you have an open HMRC enquiry into a prior year tax return, the outcome of which, will affect the reporting on your 2024/25 tax return declaration?

Generally, it is best to wait until HMRC have concluded on the treatment of an income/relief claimed. If you expect a large payment will be due to HMRC, an estimated payment of taxes can be made to minimise interest and penalties.

Are you sure the 31st January 2026 deadline applies to your 2024/25 tax return?

If you have never filed a tax return with HMRC and registered for Self assessment after the 5th October 2025, HMRC would generally allow you to file a tax return within 3 months of registration. Check your Self Assessment record to confirm the deadline that applies to you.