Claim Your Tax Back / Lesson 6 of 7
Backdating a claim
Four years is claimable. The fifth disappears every April, silently.
The short answer
- ✓ You can claim the current tax year plus the four previous ones
- ✓ Each year is calculated separately against that year's tax position
- ✓ Past years are repaid as money; the current year usually adjusts your code
- ✓ Tell HMRC when an ongoing claim stops applying, or it becomes an underpayment
The four year window
You can claim employment expense relief for the current tax year and the four previous ones. The deadline for each year is four years after the end of that tax year, and once it passes there is no discretion and no appeal.
Uniform flat rate, mechanic £120 a year
Basic rate relief at 20% £24 a year
Four backdated years £96
Plus an ongoing code increase every year afterwards
Add a mileage shortfall and the same claim is often
several hundred pounds rather than tens.Claiming several years at once
Perfectly normal, and it is how most first-time claims are made. Enter each year separately on the form. HMRC works through them individually because your tax position differed each year: a year where you paid higher rate produces more relief than a year where you paid basic rate, on identical expenses.
What a big backdated claim does to your code
Two separate things happen and people confuse them:
- Past years are repaid directly, as money
- The current year is usually handled by increasing your tax code, so take-home rises
So a successful four-year claim often produces a payment and a code change. Seeing only one of the two is not evidence that something went wrong.
The bit HMRC does not spell out
Once an ongoing expense is in your tax code it usually stays there for future years without being re-claimed. That is convenient while the circumstances hold, and a problem when they change. If you stop wearing a uniform, change to a job with no business mileage, or your employer starts reimbursing you, the relief keeps being given and you are quietly underpaying tax that HMRC will eventually reclaim.
Tell HMRC when a claim stops applying. It is the same five minutes in your Personal Tax Account that started it.
Common mistakes
- Waiting for a convenient moment. A year drops off every April.
- Claiming one year because it feels small. Claim all eligible years together.
- Expecting only a payment. Current year relief comes through the code.
- Leaving a stale claim running. That becomes an underpayment.
Try it on your own numbers
This is the same calculator as the full tool page, using 2026/27 rates.
Tax refund check
Compare the Income Tax you actually paid with what you should owe for the year.
Your total taxable income for the year (salary, pension etc.).
From your payslips, P60 or P45 (tax deducted - not National Insurance).
Left a job part-way through the year? PAYE often assumes you earned all year, so too much tax is taken.
- Income
- Personal Allowance
- Taxable income
- Tax due
- Tax paid
effective tax rate
your top tax rate
Income Tax only - National Insurance is not refundable this way. Reclaim overpaid tax via your Personal Tax Account on gov.uk.
How your tax is worked out
| Band | Rate | Income in band | Tax |
|---|---|---|---|
| Personal Allowance | 0% | £0 | |
| Total Income Tax due | |||
Tax due across income
Where the green line sits above the blue line, you have likely overpaid.
Compare saved checks
| Scenario | Tax due | Tax paid | Refund / owed | |
|---|---|---|---|---|
Key takeaways
- ✓ You can claim the current tax year plus the four previous ones
- ✓ Each year is calculated separately against that year's tax position
- ✓ Past years are repaid as money; the current year usually adjusts your code
- ✓ Tell HMRC when an ongoing claim stops applying, or it becomes an underpayment
Check you have got it
3 quick questions. No score is kept, and you can change your mind.
1. How many previous tax years can an employment expenses claim cover?
2. You claim four years successfully. What do you expect?
3. Your uniform claim is in your tax code but you have changed to a job with no uniform. What should you do?
Sources
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