One of the benefits of MTD is that after each quarterly update, HMRC provides you with an in-year tax estimate. This is a running calculation of your likely tax bill based on the income and expenses you've reported so far. Here's how to read it.
Where to find your tax calculation
After submitting a quarterly update, AffordableMTD displays your estimated tax calculation. You can also view it at any time from your dashboard or submission history. The calculation is generated by HMRC, not by AffordableMTD — we fetch it directly from HMRC's API and display it for you.
What the estimate includes
Your in-year tax calculation typically shows:
- Total income — the gross income you've reported across all your businesses (self-employment and/or property)
- Total expenses — your allowable deductions
- Taxable profit — income minus expenses
- Income Tax due — estimated tax based on the applicable tax bands (personal allowance, basic rate, higher rate)
- National Insurance contributions — Class 2 and Class 4 NIC estimates
This is an estimate, not a bill. The in-year calculation is based only on the data submitted so far. It doesn't include other income sources HMRC may know about (like PAYE employment income), and it will change as you submit more quarters. Your final, official tax liability is only determined when you file your final declaration.
Why your estimate changes each quarter
Because quarterly updates are cumulative (each one includes year-to-date figures), your tax estimate is recalculated after every submission. Expect it to:
- Increase as you report more income throughout the year
- Decrease if later quarters have higher expenses relative to income
- Fluctuate if your income is seasonal or irregular
The Q1 estimate will almost certainly look low because it's based on just three months of data. By Q4, it should be close to your actual annual liability.
What the estimate doesn't include
Until you file your final declaration, the in-year estimate won't account for:
- Capital allowances — these are claimed as end-of-year adjustments, not in quarterly updates
- Loss relief — brought-forward losses are applied at year end
- Payments on account — existing payments on account from previous years aren't reflected in the in-year estimate
- Other income sources — employment income, interest, dividends, etc. are included at the final declaration stage
This means the in-year estimate may differ from your final tax bill. It's useful for planning and tracking, but should not be treated as the definitive figure.
What to do if the estimate looks wrong
If your tax estimate seems unexpectedly high or low, check:
- Your submitted figures. Review the quarterly update you submitted — did you accidentally enter a figure in pounds rather than pence, or miss an expense category?
- The cumulative total. Remember that Q3 should include Q1 + Q2 + Q3 data combined. If you only entered Q3's figures, the calculation will be wrong.
- Multiple businesses. If you have both self-employment and property income, check that you've submitted for all businesses.
You can resubmit a corrected quarterly update at any time. The latest submission replaces the previous one, and HMRC recalculates your estimate.
Don't panic about a high estimate early in the year. HMRC's in-year calculation applies annual tax thresholds (like the personal allowance) proportionally. The numbers will settle down as more quarters are submitted. The final declaration is what actually determines your tax bill.
Track your tax position throughout the year
No surprises in January. See your estimated liability update in real time as you submit each quarter.
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