What a mileage log has to prove, wherever you file it

Four tax authorities, four rate structures, and near-identical expectations about evidence. The rate varies. What counts as a record barely does.

The Milesheet Team9 March 2023 · 3 min read

Photo by Green ChameleonCC0 1.0

Update, April 2026: the UK approved rate for cars and vans rose from 45p to 55p a mile for the first 10,000 business miles. The 25p rate above that, and the 5p passenger payment, are unchanged. This post describes the position as it stood when it was written.

The interesting thing about comparing mileage systems is how much they disagree about the money and how little they disagree about the paperwork.

The four facts, everywhere

Britain, America, Germany and France ask for the same four things about a business journey:

The date it happened
Where you went, specifically enough to identify it
Why, in business terms
How far it was

That is the whole list. There is no jurisdiction where a bare monthly total is sufficient, and none where the four facts are not enough.

Contemporaneous, and they mean it

The word that does the work is contemporaneous: written at the time, or close to it.

The IRS is the most explicit about this, asking for records made at or near the time of the journey, on the reasoning that a record made later is a reconstruction and a reconstruction is an estimate. HMRC's wording is softer but the expectation is the same in substance, and the practical test is identical: could you produce, journey by journey, something you did not invent in April?

This is the single most common failure. Not fraud, not exaggeration, just a year of driving reconstructed from a diary and a rough sense of the route, which produces round numbers, plausible distances and nothing that survives being questioned.

What makes a claim look wrong

The patterns that attract attention are also broadly shared.

Round numbers. Real journeys are 11.2 miles and 33.8 miles. A log of 10s, 20s and 50s is a log of estimates.

Totals that do not reconcile with the odometer. If your log says 8,000 miles and the car did 20,000, the gap is not itself a problem, but it should be explicable. If the log says 22,000 and the car did 20,000, that is a problem.

Commuting inside the claim. Every one of these systems excludes the ordinary commute in one way or another, and a claim that quietly includes it is the error auditors find fastest.

A claim that ends exactly at a threshold. Ending the year at 9,998 business miles is not evidence of anything, but it is the kind of coincidence that invites a second look.

What differs

Only two things, really.

Who keeps the record. In Britain and America the driver keeps it and produces it if asked. In systems built around employer reimbursement, such as Spain and Ireland, the employer's payroll records carry more of the weight, though the driver still needs to be able to justify the underlying journeys.

How long to keep it. The retention periods differ by jurisdiction, and the safe answer everywhere is longer than you think and longer than the year the claim relates to.

The practical version

The record must	UK	US	Germany	France
Date each journey	Yes	Yes	Yes	Yes
Name the destination	Yes	Yes	Yes	Yes
State the business purpose	Yes	Yes	Yes	Yes
Give the distance	Yes	Yes	Yes	Yes
Be made at the time	Expected	Explicitly	Expected	Expected
Exclude commuting	Yes	Yes	Separate allowance	Yes

Why this is an argument for automation

The four facts are easy to know and easy to lose. Three of them, the date, the destination and the distance, are things a phone in a moving car already knows. Only the reason is genuinely yours to supply.

That is the whole design argument for recording a drive as it happens rather than writing it up later: it moves three of the four facts from memory into evidence, and leaves you with one thing to add while you still remember it.