Say you cover a branch 30 miles from home three days a week. That's 180 miles a week, and over a 40-week year, 7,200 miles. At HMRC's 55p a mile, that's £3,960 you can deduct from your profits. For a basic rate taxpayer, it's around £1,030 less to pay in Income Tax and National Insurance.
Plenty of locums claim far less than they could. It isn't usually that they don't know mileage counts. It's that, come January, nobody can remember where they drove in May.
Which journeys can you claim?
As a self-employed locum, you can generally claim the cost of travelling for your business. For most locums, that means driving from home to the pharmacies you cover, because each one is a temporary workplace rather than somewhere you go every day as an employee would.
It gets less clear-cut if you work at the same pharmacy for a long stretch, week in, week out. At that point it can start to look more like a regular commute, which isn't allowable. If most of your shifts are at one place, it's worth asking an accountant how HMRC is likely to see it.
How much can you claim?
Sole traders can work out their vehicle costs in one of two ways.
- Simplified expenses, using HMRC's flat rates: for the 2026/27 tax year, 55p a mile for the first 10,000 business miles in a car or van, and 25p a mile after that. Motorcycles are 24p a mile.
- Actual costs, adding up fuel, insurance, servicing, repairs and so on, and claiming the business share of them, with capital allowances for the vehicle itself.
For most locums, the flat rate is simpler and works out well. Three things to know about it:
- The rate depends on the tax year. The first 10,000 miles were 45p a mile before 6 April 2026, so your 2025/26 return still uses 45p. From 6 April 2027, miles beyond 10,000 are due to rise from 25p to 35p.
- The flat rate covers the whole cost of running the car, so you can't claim fuel or insurance on top. You can still claim parking and tolls separately.
- Once you've used the flat rate for a vehicle, you have to keep using it for as long as you have that vehicle.
The log HMRC expects
You don't send HMRC your mileage log with your Self Assessment, but you need to keep one in case it asks. For each business journey, that means:
- the date;
- where you started and where you went;
- why you went, such as the pharmacy and the shift;
- how many miles it was.
Split days count too. If you drive from a morning shift in one town to an afternoon shift in another, that leg is business mileage of its own.
Some pharmacies also pay mileage on top of your rate. That money is part of what you've earned from the shift, so keep it on the invoice and in your records too.
Why logs go missing
Writing down a journey takes a minute. The trouble is that it's a minute at the end of a long day, every day, for a year. Most locums start a spreadsheet in April with good intentions, and by autumn it's a guess based on bank statements and an old diary.
A reconstructed log is also the hardest kind to defend. Rounded numbers and journeys that don't match your invoices are exactly what an HMRC enquiry looks for.
The reliable log is the one you don't have to write. Your shifts already say where you were and when. If something knows your home address and the pharmacy, it can work out the miles itself, at the moment the shift happens.
Want to see what your own driving is worth? The locum mileage calculator works out a year of shifts at HMRC's rates, and what it saves you in tax.
A mileage log built from your shifts is complete by default. There's no spreadsheet to keep up and nothing to reconstruct in January, and every journey matches an invoice, because they came from the same place.
This article is general information about UK tax as of November 2026, not tax advice. Your own position depends on your circumstances, so check with HMRC or a qualified accountant before you file.