HMRC mileage log requirements are shorter than most people expect. For every business journey, record the date, where the journey started and ended, why it was made, and how many miles it covered. There is no official form. Paper, a spreadsheet or an app are all acceptable, as long as somebody could check the record against the journey.
The part that surprises owners with company cars is what the log is for. It does not change the company car tax itself. What it does decide is how much you can pay drivers for fuel without creating a tax bill, whether a fuel benefit charge lands on anyone, and how much VAT on fuel you can reclaim. Those are the reasons to get it right, and they are why a logbook filled in from memory every March is costing more than it looks.
What the HMRC mileage log requirements actually ask for
For each business journey, a usable record shows:
- The date of the journey.
- Where from and where to. Full addresses or clearly identifiable places, not "Birmingham".
- The business purpose. "Site visit, Smith Road job" rather than "work".
- The miles for that journey.
- Which vehicle, if the driver uses more than one.
Two rules catch people out. The ordinary drive between home and a permanent workplace is commuting, not business, however early it starts. And a record written at the time is worth far more than one rebuilt from a diary at the end of the year. The reconstructed version is the one that does not survive questions, because nobody can explain why the totals do not match the odometer.
A mileage log will not change your company car tax
It is a common belief that more business miles means less company car tax. It does not. The benefit in kind on a company car is worked out from the car's list price and a percentage set by its CO2 emissions and fuel type. A driver who does 30,000 business miles a year pays the same benefit on the same car as one who does 3,000.
So if the log is not for the car, what is it for? The fuel, and the VAT on the fuel.
Can you claim mileage on a company car?
Yes, for the fuel used on business journeys. Where a driver pays for fuel themselves, you can pay them back for business miles using HMRC's advisory fuel rates. Pay at or below those rates and there is no tax or National Insurance on the payment. They are not the same as the rates for drivers using their own cars, and HMRC revises them every quarter.
A company car mileage claim is only as good as the business miles behind it. Without a log, you are either paying on a guess or not paying at all, and drivers notice which.
Private fuel and the fuel benefit charge
If the business pays for fuel and the driver uses some of it privately, a separate fuel benefit charge applies. It is worked out from a fixed figure HMRC sets each year, multiplied by the same percentage as the car. It is not scaled to how much private fuel was used. A driver who does fifty private miles can face the same charge as one who does five thousand.
The way out is for the driver to pay back the cost of all their private fuel, by 6 July after the end of the tax year. Paying back most of it does nothing. To know what "all" is, somebody needs the private miles, and private miles are simply the total on the odometer minus the business miles in the log. No log, no figure, and the charge stands.
The same records do quieter work on pool cars. A car shared between staff for business journeys, normally kept at your premises and not used privately, does not carry a benefit at all. A log showing business journeys by different drivers is the evidence that a pool car really is one.
Reclaiming VAT on fuel
When the business buys fuel that is used for both business and private driving, HMRC gives you a choice of how to treat the VAT, set out in its guidance on motoring expenses. You can reclaim all of it and pay a fuel scale charge, reclaim none of it, or keep detailed mileage records and reclaim the VAT on the business share only.
The third route is often the cheapest for a car that does mostly business miles, and it is the only one that needs the log. HMRC's own worked example takes the business miles, divides by the total miles, and applies that share to the fuel bill. Two numbers per car. They just have to be real.
Why paper logbooks fail
Almost every business with a handful of company cars starts with a logbook in the glovebox or a spreadsheet each driver keeps. It works in the first month. By the end of the year it fails in the same few ways:
- It is filled in at the end. In March someone asks for the logs, and a year of journeys is reconstructed from calendars and memory.
- Nobody owns the pool car. Everyone drives it, nobody writes anything down, and the miles cannot be explained.
- Cars change hands. A car moves to a new driver in October and the odometer readings either side of the handover are lost, so private miles land on the wrong person or on nobody.
- The accountant gets twelve formats. One driver's spreadsheet, another's photographed notebook, a third's "about 80%". Turning that into figures for each car is paid work.
Mileage tracking for business without the spreadsheet
We built a business mileage log into our fleet system to remove that year-end scramble. It is deliberately simple for the driver and deliberately strict about the numbers.
The driver logs a trip on their phone: from, to, purpose, and the odometer at the start and the end. The start reading is filled in from the car's last known mileage, so most trips are one reading and three short answers. The miles are worked out from the readings, not typed, and an out-and-back journey can go in as one trip.
A trip can only go on a car the driver actually had that day, or on a pool car. That one rule stops most of the errors that make year-end logs unreliable, including the handover-day problem: on the day a car changes hands, both drivers can still log their own trips.
At the end of the tax year there is a statement for each car and each driver, covering the period that driver had it: opening and closing odometer, total miles, their business miles, other drivers' business miles in the same car, and the private miles that leaves. That is exactly the split the fuel benefit, the fuel repayment and the VAT reclaim each need.
Where a figure cannot be worked out, it says so. If there is no odometer reading at the start or end of a driver's period, the private miles are left blank and flagged, rather than quietly calculated from a guess. A missing number you can see is better than a wrong one you can't.
The accountant gets their own access to the mileage log and nothing else in the fleet system, with the statement and the full trip list available as spreadsheets. They can read every trip but cannot change one. Only the driver who logged a trip can correct it, so the record stays the driver's own account of their driving.
What it will not do
It is worth being clear about the limits, because a log that does less than you assumed is worse than knowing you have a gap.
- It does not track by GPS. The driver says where they went and why. That is deliberate: a tracker can tell you where a car went, but not whether the journey was business, and the purpose is the part HMRC asks for.
- It covers cars on your fleet. Staff driving their own cars for work are paid under different rules, and those journeys are not part of this log.
- It does not work out anyone's tax. It hands your accountant reliable miles. The rates, the benefit figures and the VAT calculation stay with them.
- It cannot make a driver log a trip. It can make the gaps obvious, and a manager can see who has logged nothing since August.
Where to start
Before changing anything, ask your accountant two questions. Which of the three VAT routes are you on for fuel? And is anyone making good their private fuel by 6 July? If the honest answer to either is "not sure", the mileage log is where the answer comes from.
The mileage log is part of blu::vehicles, the fleet part of our platform, alongside the daily walkaround checks and the morning MOT and tax checks we wrote about in stop finding out a van is off the road on the morning you need it. If your company car mileage still lives in glovebox notebooks, get in touch and we will show you what a year of your own fleet's trips would look like.