Car ownership calculator
Mileage Tax Relief Calculator
Compare the approved mileage amount with employer payments received.
Use this calculator
What your result means
This compares the HMRC approved mileage amount with employer mileage payments entered. The displayed unreimbursed approved amount is a potential basis for considering relief; it is not itself cash back or a guaranteed tax refund.
Any tax effect depends on eligibility and the individual’s marginal tax position, which this calculator deliberately does not estimate.
Worked example
A car or van with 12,000 business miles and £4,500 employer mileage payments:
- Approved mileage amount
- £6,000.00
- Employer payments
- £4,500.00
- Potential unreimbursed amount
- £1,500.00
This difference is an input to a tax-relief claim assessment, not the amount a person receives.
Formula
Illustrative approved amount versus employer payments
| Business miles | Approved amount | Employer paid | Unreimbursed amount |
|---|---|---|---|
| 5,000 | £2,750.00 | £2,000.00 | £750.00 |
| 10,000 | £5,500.00 | £4,500.00 | £1,000.00 |
| 12,000 | £6,000.00 | £4,500.00 | £1,500.00 |
| 15,000 | £6,750.00 | £6,000.00 | £750.00 |
| 20,000 | £8,000.00 | £7,000.00 | £1,000.00 |
| 25,000 | £9,250.00 | £9,000.00 | £250.00 |
Read the difference carefully
An employer paying less than the approved amount does not automatically create a refund of that difference. It may be relevant when assessing tax relief, subject to HMRC rules and the person’s tax circumstances. Keep mileage and payment records and use official guidance or professional advice for a claim.
Assumptions and limitations
- Uses 2026/27 approved rates.
- Employer payments are entered as a total and are not independently verified.
- The calculator does not provide personalised tax advice or estimate tax payable/refundable.
Helpful questions
Is the unreimbursed amount my tax refund?
No. It is not a refund amount.
What does employer payment mean?
The mileage payments actually received for the business miles being compared.
Why does the calculator stop at zero?
It does not present an excess employer payment as negative relief.
Does this apply to a company car?
Usually use company-car rules and advisory fuel rates instead.
Do rates change?
They can change by tax year; confirm the current HMRC guidance.
Related calculators
- HMRC Mileage Calculator
Calculate the HMRC approved mileage amount for 2026/27.
- Mileage Reimbursement Calculator
Calculate reimbursement from business miles and an entered rate.
- Advisory Fuel Rate Calculator
Calculate 1 September 2026 company-car advisory fuel amounts.