Claiming business mileage is simple in principle and goes wrong in practice for the same handful of reasons: the log is reconstructed rather than kept, the commute is counted, the rate is applied without the 10,000 mile threshold, or a company car is claimed at the private car rate. This page is written for the employee or the fleet manager who processes the claims: what the log has to carry so that it survives an inspection, which rate applies to which vehicle, how a claim is checked before it is paid, and the four mistakes that turn a tax-free expense into taxable pay. The worksheets on this site apply the rates; the log is the driver's.
A log that survives inspection
Every business journey needs the date, where it started and ended, why it was made and how far it was, recorded when it happened. Odometer readings at the start and end of the year help. A log built at the year end from a diary is the first thing an inspector doubts, and a claim with round numbers every month is the second. A mileage app or a notebook both work; the discipline is the same.
Which rate applies
The driver's own car, including one funded by a car allowance, uses the approved mileage rate: 55p a mile to 10,000 business miles in the tax year, then 25p. A company car uses the advisory fuel rate for its fuel and engine size, or the electricity rate for a company electric car. Claiming a company car at the private car rate is the commonest error in a mixed fleet, and the excess is taxable.
Checking a claim before paying it
Does every journey have a purpose that is work rather than commuting? Does the running total for the year show whether the driver has crossed the threshold? Is the vehicle the driver's own, and is the rate the right one for it? Is any passenger payment at the passenger rate and only for a colleague on business? A claim that passes those four questions can be paid tax free up to the approved amount.
The four mistakes
Counting the commute, which is never business mileage. Paying a flat rate above the approved rate, which makes the excess taxable pay from the first mile. Ignoring the threshold, which overpays a high-mileage driver in the second half of the year. And paying a company car driver the private car rate, which is a taxable payment for fuel they did not buy. Each is a payroll correction and a P11D entry waiting to happen.
Questions people ask about claiming business mileage
Can I claim business mileage without a log?
You can submit one, but the employer's payment and any relief claim rest on evidence of the miles; without a log an inspector can treat the payment as taxable pay.
Is a mileage app acceptable to HMRC?
Yes, provided it records the journeys as they happen with date, route, purpose and distance. The format is not prescribed; the content and the timing are.
Who is responsible if a claim was wrong?
The employer, for the tax and National Insurance on any excess it paid, and the driver, for any relief wrongly claimed from HMRC. Both are put right by correcting the year's figures.