Cumulative Quarterly Updates: HMRC's New MTD Submission Model Explained

If you've read older guides about Making Tax Digital, you might have seen references to "standalone" quarterly updates — submitting just that quarter's figures four times a year. That model is gone. Since April 2025, HMRC moved to a cumulative submission model, and it's how every MTD ITSA quarterly update now works.

What changed

Under the old (standalone) model, each quarterly submission contained only the figures for that specific three-month period. If you made a mistake in Q1, you had to submit a separate amendment for Q1 to fix it.

Under the new cumulative model, each submission contains your year-to-date totals. Q1 covers 6 April to 5 July. Q2 covers 6 April to 5 October — the whole period from the start of the tax year, not just July to October. Q3 covers 6 April to 5 January, and Q4 covers the full tax year up to 5 April.

Why the change?

HMRC switched to cumulative submissions to make corrections trivially easy. Spotted an error in your Q1 figures when you're preparing Q2? You don't need a special amendment — just submit your Q2 update with the correct year-to-date numbers, and the corrected total replaces whatever was there before.

It also reflects how most sole traders and landlords actually think about their finances — you don't reset your books every three months, you watch your year-to-date numbers grow.

How it works in practice

Imagine you're a freelance designer with these quarterly turnovers:

• Apr–Jun: £8,000 turnover, £1,500 expenses
• Jul–Sep: £12,000 turnover, £2,200 expenses
• Oct–Dec: £9,500 turnover, £1,800 expenses
• Jan–Mar: £14,500 turnover, £3,000 expenses

Your four MTD submissions would contain:

• Q1 (due 7 Aug): Turnover £8,000, Expenses £1,500
• Q2 (due 7 Nov): Turnover £20,000, Expenses £3,700
• Q3 (due 7 Feb): Turnover £29,500, Expenses £5,500
• Q4 (due 7 May): Turnover £44,000, Expenses £8,500

Each submission replaces the previous one. HMRC always has the latest year-to-date snapshot.

What if you spot a mistake?

Just resubmit. There's no separate amendment process and no penalty for correcting your own figures before the Final Declaration. Submit a fresh cumulative update with the right numbers, and the previous submission is overwritten.

You can resubmit as many times as you want during the tax year. HMRC just keeps the most recent one.

What about Q4?

Your Q4 submission (due 7 May after the tax year ends) is your final cumulative quarterly update — the full year's figures. It's not your Final Declaration; that's a separate end-of-year submission that confirms everything and triggers your tax bill. Some bridging software (Flonancial included) only handles the four quarterly updates and signposts you to HMRC for the Final Declaration.

The practical takeaway

You don't need to track quarter-by-quarter increments separately. Your spreadsheet just needs to show your running totals from 6 April. Each quarter, upload it, and Flonancial sends the latest year-to-date figures to HMRC. That's the whole process.