How to claim mileage on Self Assessment
Quick answer
Claim mileage allowance on Self Assessment form SA103F (self-employment pages). Multiply business miles by AMAP rate (55p first 10k, 25p thereafter for cars). Enter total in box 31 "motoring expenses". You cannot claim actual vehicle costs if using mileage allowance.1
Step-by-step process
- Calculate total business miles for tax year (6 April to 5 April)
- Apply AMAP rates: (first 10,000 × 55p) + (remainder × 25p)
- Enter total in SA103F box 31 "motoring expenses"
- Keep mileage log for 5 years
What records to keep
- Date of each journey
- Start and end locations
- Purpose of journey
- Miles travelled
Common mistakes
Do not mix mileage allowance with actual costs. If you claim 55p per mile, you cannot also deduct fuel receipts or insurance. It's one or the other.1
Sources
- HMRC (2025). Self Assessment: self-employment (SA103F). gov.uk (accessed 10 July 2026)