Making Tax Digital for Income Tax
I sent my quarterly update with the wrong figures
The first ever MTD for Income Tax quarterly update was due on 7 August 2026, and a lot of them were assembled in a hurry. The good news is the one the software adverts skip: for the first three updates of the year there is usually nothing to amend at all. Quarterly updates restate the tax year to date, so correcting your records is enough — the next update carries the fix.
Which situation are you in?
Why an error usually fixes itself
This is the part that surprises people, and it is the single most useful thing to understand about MTD. A quarterly update is not a return for a three-month slice of the year. gov.uk puts it plainly: each quarterly update covers from the start of the tax year to the end of the update period, not just the previous three months.
So your second update does not report July to October. It reports 6 April to 5 October — the whole year so far, restated. Whatever you send in November simply supersedes what you sent in August. If the August figures were wrong and your records are now right, the November update carries the corrected totals and the earlier mistake stops existing.
That is why gov.uk says you will not need to resend a quarterly update separately after making an adjustment: your software includes the correction in subsequent updates automatically. There is no amendment form, no correction window and no catch-up submission for the first three quarters of a year.
The one thing you do have to do
Fix the digital records themselves, and do it now rather than in January. gov.uk asks you to correct your digital records as soon as you become aware of an error, and that duty is separate from anything you send. The correction only reaches HMRC if it is in the records when the next update is generated.
The two exceptions
The cumulative mechanic runs out in two places, and both are worth knowing before you need them.
The fourth update. It is the last restatement of the year, so there is nothing after it to carry a correction. gov.uk names this case directly: you may need to resend your fourth quarterly update if you need to make changes to your digital records.
After the final declaration. Once the final declaration is in, the quarterly updates are history — the declaration is what your tax was actually calculated from. From that point the vehicle is a tax return amendment, and gov.uk allows a correction within 12 months of the Self Assessment deadline. For 2026/27 the return is due 31 January 2028, so the window closes on 31 January 2029.
What it costs
Nothing, in almost every case — but the reasons differ, and the distinction matters if you owe more tax as a result of the correction.
| Situation | Cost in 2026/27 | Points? |
|---|---|---|
| Wrong figures in a quarterly update | Nothing — no payment or tax is calculated from it | No |
| A quarterly update sent late | None at all this tax year | No |
| The 2026/27 tax return late (due 31 Jan 2028) | Penalty points apply | Yes |
| Extra tax paid 16–30 days late | 3% of the tax outstanding at day 15 | — |
| Extra tax paid 31+ days late | 3% + a further 3%, then 10% a year interest | — |
Late payment percentages rise to 4% + 4% from 2027/28. The points regime for quarterly updates — one point per missed deadline, £200 once you reach four — also starts from 2027/28. These figures are set out in HMRC's penalties for Making Tax Digital for Income Tax guidance.
The trap is the last two rows. If your correction increases what you owe, late payment penalties and interest run from the original due date, not from the date you spotted the error. Correcting a quarterly update costs nothing; underpaying the tax does.
Common questions
How do I amend an MTD quarterly update I have already sent?
For the first three updates of a tax year, you generally do not. Correct the figures in your digital records and your next quarterly update carries the correction, because each update reports the tax year to date rather than a single quarter. gov.uk states that you will not need to resend a quarterly update separately after an adjustment — subsequent updates include it automatically.
Will I be fined for getting a quarterly update wrong?
No penalty arises from the update itself. A quarterly update carries no payment and no tax calculation — it is a report of income and expenses, and your tax is worked out later at the final declaration. There are also no penalties at all for a late quarterly update in the 2026/27 tax year. What is not waived is the accuracy of the return, and the penalties and interest on tax paid late.
What if the mistake was in my fourth quarterly update?
That is the exception. The fourth update is the final restatement of the year, so no later update exists to carry a correction, and gov.uk says you may need to resend it. If your software will not let you, the correction can still be made in your final declaration, which is what your tax is calculated from.
I have already filed my final declaration. Can I still fix it?
Yes, by amending the tax return rather than the quarterly update. gov.uk allows a correction within 12 months of the Self Assessment deadline. For 2026/27 the deadline is 31 January 2028, which gives you until 31 January 2029. If the amendment increases your tax, pay the difference promptly — interest runs from the original due date.
I overstated my income. Will I get the overpaid tax back?
You will not have overpaid anything on the strength of a quarterly update, because no tax is due on one. Your liability for 2026/27 is calculated only at the final declaration, from the figures standing at that point. Correct your records and the right number is the one that counts.
Do I need to tell HMRC I made a mistake?
Not for a routine correction to a quarterly update — the mechanism is the next update, not a disclosure. That is a different question from a deliberate or material understatement on a return, where HMRC's disclosure routes exist and an accountant is worth the fee. This page covers ordinary errors: a transposed figure, a missed invoice, an expense in the wrong category.
My software will not let me resend. Is that a problem?
Usually not. Resending an individual earlier update is not the mechanism for the first three quarters anyway — the next cumulative update is. Software behaviour varies most at the fourth update and at the final declaration, which are the two points where a resend genuinely matters. If yours will not support it there, the final declaration is the backstop.
The figures were wrong because the records were loose
Almost nobody mistypes a total. The errors in a first quarterly update come from somewhere else — an invoice that was never logged, an expense sitting in the wrong month, a bank line nobody categorised. The update was just the moment it showed up. There are three more of these before January, on the same three-month rhythm, and each one restates everything that came before it.
- Self Assessment Tax Estimator 2026/27 — know what you owe before January, not after.
- Invoice Tracker & Log — auto paid/outstanding/overdue, so nothing goes unlogged.
- Freelance Day-Rate & Profit Calculator — works backwards from the take-home you want.
- Rental Property ROI & Yield Calculator — including Section 24 and a rate stress test.
Excel and Google Sheets. Working formulas, not just formatting. They keep the digital records MTD expects and total themselves, so the next update is a copy-and-paste — you'll still need bridging software to send it, and we don't pretend otherwise.
An accountant or bookkeeper? Because the next update restates the year to date, a wrong figure fixes itself — but only if someone corrected the records before the next deadline. Across a client list that is the actual job: knowing whose figures were amended and whose are about to carry the same error into the next quarter. The MTD Practice Tracker keeps every client's four updates and final declaration on one board. £39 one-time.
See the toolkit — from £9 →Four working spreadsheets. £9 each, or all four for £19, with a 14-day money-back guarantee.