MilometryYour fleet tracker is not your mileage log
A telematics box knows where the van went and how far. It does not know why, and why is the part a tax authority asks about. What tracker data can prove, what it cannot, and what an employer must tell you about it.
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A lot of company vans and cars now carry a telematics box: a small unit wired behind the dashboard that records position, distance, time and often speed and harsh braking. Fleet managers like them for routing, fuel and insurance. Drivers sometimes assume that, because the box records every mile, the mileage claim takes care of itself.
It does not, and the reason is simple. A tracker records where a vehicle went. A tax authority wants to know why.
What the tax authorities ask for
United Kingdom. HMRC's guidance for employees claiming tax relief on a vehicle they use for work says to keep records of the dates and mileage of your work journeys, and that a mileage log sent with a claim must show, for every journey, the reason for it, the postcode where it started and the postcode where it ended.
United States. IRS Publication 463 lists the elements for car expenses: the mileage for each business use and the total miles for the year, the date of each use, the business destination and the business purpose. It also says the record should be made "at or near the time" of the use, that a weekly log counts as timely, and that a record kept on a computer is an adequate record.
Line those up against a telematics export and most boxes are already there on date, start point, end point and distance. Some are more precise than a hand-written log ever was. The gap is the purpose column, which is the one that decides whether a trip is business travel or ordinary commuting.
Why purpose is the whole question
The same drive can be claimable on Monday and not on Tuesday. A trip from home to a client's site is usually business travel. The same trip to a permanent workplace is commuting, and commuting is private. A tracker cannot tell the difference, because the difference is not in the road; it is in what you were going there to do. We covered where that line falls in what counts as a business mile.
So a tracker export on its own is a list of journeys, not a claim. It becomes evidence once each journey has a purpose attached, ideally added at the time, or within the week, as the IRS puts it.
Where tracker data genuinely helps
- Distance you can stand behind. Odometer-to-odometer or GPS distance beats a guess from a route planner, and an estimate is exactly what the IRS says you cannot deduct.
- Total miles. The IRS asks for total annual miles as well as business miles, so it can see the split. A tracker records both without effort.
- Back-up for a query. If a log is ever questioned, an independent record of the same journeys on the same dates is useful corroboration.
Treat it as the spine of the log, then add the reason for each business trip.
The other side: what your employer must tell you
In the UK, a tracker in a vehicle you drive is processing your personal data, and the Information Commissioner's Office says so plainly in its guidance on monitoring workers: telematics data that records a driver's activities is personal information and is covered by data protection law.
The same guidance says employers must inform workers and passengers of any vehicle monitoring. Where a work vehicle can also be used privately, it says monitoring during private use will rarely be justified, and its worked example is a tracker the driver can switch off outside working hours. Monitoring driver behaviour, or adding cameras or audio, is treated as high risk and needs a data protection impact assessment first.
None of that stops an employer using tracker data to check a mileage claim. It does mean you are entitled to know the box is there, what it records and what it is used for.
The short version
A telematics box answers where, when and how far. A mileage log has to answer why. Keep the tracker data, because it makes the distances hard to argue with, and keep your own note of the purpose of each business trip, because that is the part nobody can record for you.
General information, not legal or tax advice. Rules differ by country and change over time, so check your own position with the tax authority or a qualified adviser.
