Can You Backdate Mileage Claims on Your Self Assessment?
Yes, you can backdate mileage claims – but there’s a strict time limit. HMRC allows amendments for up to four years after the end of the relevant tax year. If you missed claiming in a previous year, you can still claim expenses for that period as long as you are within the four-year window.
This period starts from the 31st January deadline following the tax year in question. For the 2019/20 tax year, you have until 31 January 2025 to make amendments.
Once this four-year window closes, you permanently lose the opportunity to claim that tax relief. It’s worth checking previous years if you think you’ve missed expenses or something else.
I once discovered I’d forgotten to claim nearly 2,000 business miles from two years prior. The backdated claim allowed me to claim expenses for previous years and saved me over £400 in tax – money I would have lost without checking.
What Evidence Do You Need for Backdated Mileage Claims?
For backdated claims, good record-keeping becomes even more important. HMRC may want proof these journeys actually took place.
Ideally, you should have a mileage log showing dates, destinations, distances, and the business purpose of each trip. Make sure to include precise details such as the start point and miles travelled for each journey. Even creating this retrospectively is better than nothing.
Supporting evidence might include your appointment calendar, client meeting notes, or emails confirming appointments. Work diaries showing your location can also help. You should also document the business portion of each journey to demonstrate that only business-related mileage is being claimed as an expense.
If you’re claiming actual vehicle expenses rather than mileage rates, you’ll need receipts for fuel, insurance, and repairs from that period. Only expenses that were personally paid can be claimed. Professional fees and other total expenses also require supporting evidence to be accepted by HMRC.
Understanding Claiming Tax Relief
Claiming tax relief on your business expenses, including mileage allowance, is a powerful way to reduce your tax bill and potentially increase your tax rebate.
To qualify, your expenses must be incurred wholly and exclusively for business purposes—this covers costs like fuel, maintenance, insurance, and other running costs for your vehicle.
You have two main options for claiming tax relief on vehicle expenses: the actual costs method or the simplified expenses scheme. The actual costs method involves claiming the precise costs you’ve incurred, supported by receipts and records. The simplified expenses scheme, on the other hand, lets you claim a flat rate per mile for your business mileage, making it easier to manage and less time consuming.
Whichever method you choose, keeping accurate records is crucial. Use accounting software or consult a tax professional to ensure you’re claiming the correct amount of tax relief on your self assessment tax return. Understanding the rules around allowable expenses and the difference between business and personal journeys will help you maximise your claims and boost your business profits.
By staying organised and using the right claiming method for your situation, you can make the most of your tax relief opportunities, reduce your tax liability, and keep more money in your business.
