Cumulative MTD updates: why a Q1 mistake is not a disaster

The single most reassuring thing about Making Tax Digital is the least advertised: quarterly updates are cumulative. Each one reports your totals from the start of the tax year to the end of that quarter. The second update contains everything in the first; the fourth contains the whole year. HMRC keeps the latest one and forgets the rest.

What that means in practice

Suppose you sent your first update with £6,000 of rent and £900 of expenses, then found an £180 boiler repair receipt from June in a drawer. You do not amend the first update. You add the receipt to your records, and the second update, which covers April to October, simply includes it. HMRC sees the corrected year-to-date figure and no one has to explain anything.

The same applies to:

• rent that was paid late and landed in the next quarter;
• an expense you categorised wrongly and moved;
• a transaction you missed entirely;
• a figure you typed with a zero too many.

As long as the correction is in your records before the next update, it flows through automatically.

A worked example

Update 4 is, in effect, your property accounts for the year. The final declaration, due by 31 January after the tax year ends, confirms those figures and adds anything MTD does not collect quarterly: employment income, dividends, pension contributions, Gift Aid and the like.

What cumulative updates do not fix

Two things still need care. First, deadlines are per update: a corrected figure in update 2 does not excuse a late update 1. Second, the final declaration is the point of no return for the year; after it is filed, changes go through an amendment rather than the next update. Get the records right during the year and the declaration is a formality.

MTDFox shows the year-to-date column next to every quarter so you can see exactly what HMRC will receive before you send it. The deadlines guide has the dates; the landlord guide covers the categories HMRC expects.