“Please update your Self Assessment tax return with final figures.”

Why you got this. ICAEW reported in March 2026 that HMRC was writing to taxpayers who had included provisional figures in their 2024 to 2025 Self Assessment return and had not yet updated it with the final figures.

In HMRC’s own word this is a reminder. The paragraph says the return included one or more provisional figures, and says nothing more about them.

Provisional figures are allowed. The arrangement is that they get replaced. HMRC’s manual says returns that include provisional or estimated figures should be accepted, provided they can be regarded as satisfying the filing requirement.

HMRC’s manual says its return guidance advises taxpayers to put provisional figures in a return rather than delay it, provided the figures are reasonable and take account of all the information available.

GOV.UK says that when you find out the final figure for a profit you used provisional figures for, you change your return, and you have 12 months from the Self Assessment deadline to make the change.

What HMRC ties to updating on time. HMRC’s sentence ties two things to updating on time: no enquiry, and no interest on tax you may owe.

GOV.UK says that if more tax turns out to be due, you pay interest on the difference between your estimates and the final figures, worked out from the original due date for payment.

GOV.UK says the Self Assessment tax bill is due by midnight on 31 January following the tax year, which for the 2024 to 2025 tax year was 31 January 2026.

GOV.UK says that after you amend a return online you see the amended bill straight away, and within 3 days your statement also shows the difference from the old bill and any interest.

HMRC’s date is its ask; the law’s time limit is a separate date. ICAEW reports that HMRC gave the taxpayer 35 days from the date the letter was issued to take the action in it.

Section 9ZA of the Taxes Management Act 1970 says an amendment to a Self Assessment return may not be made more than twelve months after the filing date.

GOV.UK gives the example that for the 2024 to 2025 tax year you will usually need to change your return by 31 January 2027.

HMRC’s date is its own ask. The law’s own time limit, in the sentences above, is a separate date the letter does not name. The consequence HMRC names in the letter is in the paragraph below the steps.

The step that applies even if your figures were right: the third. ICAEW says that where the provisional figures are now final, the update HMRC asks for is to remove the tick on box 20 of the return.

HMRC’s manual places box 20 in the ‘Finishing your Tax Return’ section of the return, on page TR7 (page TR8 from 2025 to 2026).

How a return is changed. GOV.UK says to change a return online you sign in to your tax account, open your Self Assessment account, choose ‘Tax return options’ and the tax year, then go into the return, make the corrections and file it again.

GOV.UK says you must wait 3 days (72 hours) after filing before updating a return online.

GOV.UK says that if you used commercial software you contact the software provider for help correcting your tax return, and contact HMRC if the software cannot make corrections.

What “may open an enquiry” means. HMRC’s manual says that if the final figures are not provided it will take appropriate action to obtain them, and in some cases this will mean opening an enquiry.

Section 9A of the Taxes Management Act 1970 says HMRC may enquire into a Self Assessment return if it gives notice of its intention to do so.

HMRC’s factsheet CC/FS1a says a compliance check lets HMRC check your tax position: that you are paying the right amount of tax at the right time and getting the right allowances and tax reliefs.

This is an offer of help, and a team exists for it. GOV.UK says you can get extra support from HMRC if your health condition or personal circumstances make it difficult when you contact HMRC.

GOV.UK says you can get an appointment with the extra support team by asking your adviser when you call an HMRC helpline, using the extra support team webchat service, or using British Sign Language or an online form for home visits.

The manual page HMRC points to. In HMRC’s manual a provisional figure is one supplied while the final, accurate figure is still to come.

In HMRC’s manual an estimated figure is different: it is one the taxpayer wants accepted as the final figure because an accurate figure cannot be given, for example where records have been lost.

For estimated figures the manual says the taxpayer is not required to tick box 20 but should say in the ‘Any other information’ box why estimated figures were used.