How cumulative updates work, and fixing mistakes

Making Tax Digital uses a cumulative model: each quarterly update sends your figures for the whole tax year so far, not just the latest three months. That makes corrections easy. You almost never amend a past update directly; instead you fix the underlying record and your next update brings everything up to date automatically.

What "cumulative" means

Under Making Tax Digital, a quarterly update is not a standalone three-month snapshot. Each update is cumulative: it sends HMRC your income and expenses for the whole tax year so far, from the start of the year up to the end of that quarter. The four standard quarter periods are 6 April to 5 July, 6 July to 5 October, 6 October to 5 January, and 6 January to 5 April.

Because every update carries the full year to date, a later update supersedes an earlier one. Whatever you send in a later quarter becomes the current position for the year, replacing what the previous update said.

The app builds these figures for you automatically from the transactions you have recorded (whether you typed them in or brought them in by CSV import). You do not type quarterly totals anywhere: on the Send update to HMRC page you review the Cumulative figures · year to date cards, then submit.

Note: This cumulative model applies to tax year 2025-26 onward. The app reads which quarters exist, and which are due, from HMRC, and shows your due dates on the Filing Calendar.

Fixing a mistake: the normal way

This is the part that surprises people: most corrections need no special "amend" step at all.

1. Find and fix the record. If a transaction is missing, add it. If one is wrong (wrong amount, date, or category), edit it. See Recording income and expenses.
2. Submit your next outstanding quarter as usual. Open Send update to HMRC, pick the quarter, and submit.
3. The correction is included automatically. Because the new update is cumulative, it carries the corrected year-to-date totals. The earlier figure is superseded, so you do not need to go back and re-file the quarter where the mistake happened.

Tip: There is no "go back and amend Q1" button for Q1, Q2 or Q3, and you do not need one. Correct the underlying transaction and let the next update self-correct.

If you have already filed all four quarters

Once all four quarterly updates for a year are filed (you will see All 4 quarterly updates filed), you cannot re-file an earlier quarter: HMRC's cumulative model does not allow an earlier period's figures to be changed in place.

If you spot something before you finalise the year, the one in-place correction available is to re-send the final quarter:

1. The app surfaces a Go to Q4 re-submission prompt.
2. Open Q4 and choose Re-submit Q4 to HMRC.
3. Confirm in the Confirm Q4 re-submission dialog. This sends fresh year-to-date totals for the whole year.

Anything still to put right after that is handled when you finalise the year: see Reconciliation and Year-End and your Final Declaration.

Why you do not need to be perfect each quarter

Quarterly updates are estimates that you finalise at year-end. They are there to keep HMRC roughly up to date through the year, not to be your final, exact tax position. You make any annual adjustments and reliefs at year-end, and then your Final Declaration confirms the figures (replacing the Self Assessment return for the income the app covers).

So aim for accurate records as you go, but do not stall a quarterly update worrying that a figure might change later: that is exactly what the cumulative model and the year-end step are designed to absorb.

If something goes wrong

• You cannot re-submit an earlier quarter (Q1, Q2 or Q3) after all four are filed. This is expected: HMRC's cumulative model will not let an earlier period's figures move. Use Re-submit Q4 to HMRC with revised year-to-date totals, or make the correction at year-end.
• A correction is refused with an "amendment window has closed" message. Amendments are only accepted within HMRC's window. The exact timing is set by HMRC and can change, so check it with HMRC or your accountant rather than relying on a fixed rule.
• "A submission for this period is already in progress." A submission is still being processed (perhaps from another tab). Wait a few seconds, then try again.
• The figures on the update do not match what you expected. Check that the corrected transaction saved against the right property or business, with the right date and category, then reopen Send update to HMRC so the Cumulative figures · year to date cards rebuild from your records.

For the full step-by-step on sending an update, see Submit a quarterly update.

Frequently asked questions

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