How to Correct a Mistake in an MTD Quarterly Update

The Rule: Correct the Record, Not the Update

GOV.UK names the two mistakes people make. You may need to correct a digital record if you "made a mistake when creating a digital record" or "forgot to record income you received, or expenses you incurred".

The fix is the same for both: "To correct your records, you may need to change, delete or create a digital record. If you make the correction during the tax year, it will be fixed when you send your next quarterly update."

That works because an update is not a three month figure. Each one covers the tax year so far, from 6 April to the end of the period, and GOV.UK gives the reason: "This is so you can make any corrections to your records if you need to, which will then be included in your next update." The guide to what a quarterly update is shows how the totals build through the year.

So there is no amendment form for a quarterly update and nothing to send to HMRC about the earlier quarter. The earlier update is replaced by the later one.

When to Make the Correction

GOV.UK says "If you find an error or missing information in your digital records, you should correct it as soon as possible", and "After making the correction, it will be included when you send your next quarterly update."

You are not required to send anything early. The corrected figures go to HMRC with the next update, on its normal deadline.

You may send one sooner if you want HMRC's estimate of your tax to reflect the change. GOV.UK says "You can choose to send updates more often", and that most software allows it on any day. Each one still covers the tax year so far.

After the Fourth Quarterly Update

After the fourth update there is no next one to carry a correction. GOV.UK gives two ways to make it. You can choose "correcting the digital record and resending your fourth quarterly update", which it says "may be easier if you are a sole trader or landlord that keeps their own digital records". Or you can choose "adjusting the category total in your software and also reflecting it in your digital records", which is how an agent may do it before asking you to update your records.

There is an order to keep. GOV.UK says "If needed, you should resend your fourth quarterly update before you make any tax adjustments", and "If you have already sent your fourth quarterly update, you will need to make any corrections before you finalise your Income Tax position."

The same resend is used for two things that are not mistakes: adding the expenses of a jointly let property if you sent income only during the year, and recording Rent-a-Room income if you decided to claim the relief after the year ended.

Before and After the Tax Return

Before the return is submitted, a mistake in income or expenses is still a records matter. GOV.UK says "If you need to change information related to your digital records before you submit your tax return, you should correct your digital records instead of making a change to your tax return."

After the return is submitted, you change the return itself, in your software. GOV.UK says "You can make a change to a tax return within 12 months of the submission deadline." For the 2026 to 2027 tax year the deadline is 31 January 2028.

The return is where accuracy is declared. GOV.UK describes quarterly updates with the words "they are summaries, not tax returns", and it is the return you submit "by declaring that your information is correct and complete to the best of your knowledge".

The Update HMRC Refuses: An End Date That Moves Backwards

One way of correcting a quarter does not work. If you have sent the update to 5 October and then send one that ends on 5 July, to put the first quarter right, HMRC refuses it. HMRC already holds figures for that business up to a later date in the same tax year, and an update cannot end earlier than that.

You do not need the earlier one. Correct the records and send the update for the latest period HMRC holds, or a later one. It covers the year so far, so the first quarter's figure is corrected inside it. FileThat shows HMRC's refusal with a link to the help page on the submission end date cannot move backwards.

If You Keep Your Records in a Spreadsheet

The rule is the same and the place is different. GOV.UK says that if you create digital records in separate record-keeping software, for example a spreadsheet, "you should make the correction there and then digitally link your records to your bridging software".

In FileThat that means correcting the spreadsheet and uploading it again on the update, using "Upload from a spreadsheet". The totals in the file replace the figures for the tax year so far, so they must be your totals from 6 April, not for one quarter. Correct the spreadsheet only: a correcting record added in Digital Records as well would make the same correction a second time. The bridging software page explains how the upload works.

How to Correct a Mistake in FileThat

This part is FileThat, not GOV.UK. What you do depends on whether the record has already gone to HMRC in an update.

A record that has not been filed yet can be edited or deleted in Digital Records in the usual way. So can a record you left out: add it with the date it happened, and it is included in the next update you send.

A record that has been filed is locked. It shows a padlock with the words "Locked: included in a submitted return", and it cannot be edited or deleted. FileThat keeps it because the figure HMRC holds was built from it. You correct it by creating a new record that reverses the mistake, which is the third of GOV.UK's three options: change, delete or create.

If the amount was too high, add a record in the same category for the difference, with a minus sign. A phone bill entered as £500 that was really £300 is corrected by a record of -£200 under the same category. If a record was entered twice, add one for the whole amount with a minus sign. If a cost went under the wrong category, add a minus record in the wrong category and a matching record in the right one. Say what it corrects in the description, so the records still explain themselves later.

Give the correcting record the same date as the record it corrects. An update takes in a record by its date, so a correction dated after the end of the period you send is not in that update, and one dated after 5 April belongs to the next tax year. If the original record had a business-use percentage, give the correcting record the same percentage, so that it reverses the same share.

Then send. If the next quarter is due, send it as normal and it carries the correction. To send the correction now, open Your Filing Deadlines and choose Amend Return on the latest period HMRC has marked as met. The figures start from what HMRC already holds, and the records not yet filed that are dated up to the end of that period are put on top. Only the latest met period can be amended; an earlier one shows "A later fulfilled submission exists. Amend the latest fulfilled period only." HMRC can take up to an hour to mark a period as met after you send it.

All of this is about your Income Tax figures. If you are VAT registered and the same mistake went into a VAT return you have already sent, that return is put right under HMRC's VAT rules, not by a quarterly update.

Every update HMRC accepts, amendments included, leaves a receipt under Proof of Submission showing the figures that were sent.

What a Correction Costs in FileThat

One credit covers one new quarterly update, or one VAT return that is not a NIL return. Nothing else uses a credit. Sending a period again to correct it is not a new quarterly update, so Amend Return takes no credit, however many times you use it.

If you leave the correction to travel with your next quarterly update, that update costs what it would have cost anyway: one credit for each business you send it for. The correcting records themselves are free, as all record keeping is. The pricing page has the price of a credit.

If You Are an Agent

GOV.UK puts the duty plainly for agents preparing a client's return: "If you find an error or notice that information is missing, you must correct the information." Where the client keeps the records, that usually means asking them to correct the record, or adjusting the category total and asking them to bring their records into line.

In FileThat you review a client's records from your Client Portal and flag the ones that need correcting. See how FileThat works for accountants.