MTD cumulative quarterly updates explained (and how to fix a mistake)
Short answer: Every Making Tax Digital quarterly update is cumulative. It covers your income and expenses from 6 April to the end of the update period, not just the latest three months. If you find a mistake, you fix your records and the correction flows into your next update.
What “cumulative” means
GOV.UK says each quarterly update covers “from the start of the current tax year (6 April) to the end of the update period”. So the second update contains the first quarter and the second quarter added together. The third contains the first three quarters, and so on.
The updates are summaries, not tax returns. HMRC does not receive individual receipts or invoices, only a total for each category. You must send an update even if you had no income or expenses in the period. The deadlines are 7 August, 7 November, 7 February and 7 May.
Each update still covers the whole year so far if you choose calendar quarters. The periods then end on 30 June, 30 September, 31 December and 31 March, so the third update covers the year so far up to 31 December.
The old per-quarter idea
You may see older advice, or older HMRC technical documents, that treat each update as a separate three-month block. HMRC’s developer documentation still has separate per-period endpoints for tax years up to 2024-25, and cumulative ones from 2025-26. For 2026-27 and later, the cumulative model is what applies. If a template or video tells you to send “just this quarter”, it is out of date.
Worked example over four quarters
Example: Sam, a plumber and sole trader, uses standard quarters in 2026-27. The numbers are made up and rounded.
| Update | Period covered | Turnover sent | Expenses sent | Turnover in the quarter alone |
|---|---|---|---|---|
| 1 | 6 Apr to 5 Jul | £8,000 | £2,500 | £8,000 |
| 2 | 6 Apr to 5 Oct | £17,000 | £5,500 | £9,000 |
| 3 | 6 Apr to 5 Jan | £27,000 | £9,000 | £10,000 |
| 4 | 6 Apr to 5 Apr | £40,000 | £13,000 | £13,000 |
Look at the “sent” columns. Each figure is the running total for the year. By update 4, Sam has reported £40,000 of turnover and £13,000 of expenses for the whole tax year, which is the picture HMRC needs before the final declaration.
Each category works the same way. If Sam spent £1,200 on van costs in the first quarter and £800 in the second, update 1 shows £1,200 and update 2 shows £2,000.
The common spreadsheet mistake
Many people keep one tab per quarter. When the second deadline comes, they total only the second tab and send £9,000 of turnover instead of £17,000.
Because the update is cumulative, HMRC treats the latest figure as the total for the year so far. Sending only the quarter’s figures understates income by everything earned before it. In Sam’s case, using only the quarter at update 3 would report £10,000 instead of £27,000, a gap of £17,000.
The fix is to add a “year to date” tab or column that sums every quarter from 6 April. Tools that read a full-year bank CSV, such as SendMTD (not yet launched), are designed to avoid the problem by recalculating from 6 April each time. See spreadsheets and bank statements for what counts as a proper digital record.
How to correct an error
GOV.UK says that if you spot a mistake in a record, you should correct your digital records as soon as possible. The correction is included in your next update, so you do not need to resend earlier ones.
Example: Sam notices after update 2 that £500 of materials was left out of the first quarter. Sam adds the £500 to the records. Update 3 now shows £9,500 of expenses instead of £9,000, because the total from 6 April includes the corrected figure.
You can also send an update more often than quarterly. GOV.UK gives the example of sending updates for 6 April to 5 May, 6 April to 5 June and 6 April to 5 July. Each one still starts on 6 April. If you would rather not wait, sending another cumulative update with the corrected totals is a normal thing to do.
What happens at year end
The fourth update closes the quarterly cycle, but it can still be resent. GOV.UK says you may need to resend it after the tax year ends to correct errors in your records, to record joint property expenses you left out earlier, or to record Rent-a-Room income if you claim that relief afterwards. Resend it before you make any tax adjustments.
After that, you check whether any adjustments or allowances apply, add other income sources if your software does not already have them, and send your final declaration by 31 January after the tax year. What goes in an update explains which figures are left to this stage.
Whether a late update earns a penalty point depends on the tax year and when you joined: see MTD penalties. Not sure whether you are in scope? Use the MTD checker.
Sources
This guide is general information, not tax or legal advice. Rules can change: check GOV.UK or speak to an accountant about your situation. SendMTD is not affiliated with HMRC.