How to keep a mileage log for taxes

What a mileage log has to contain

Wording differs between countries, but the substance is remarkably consistent. For each business trip, a log is expected to show:

• The date you made the trip.
• The business purpose — who you saw or what you were doing, not just "work".
• The distance driven, ideally from odometer readings rather than an estimate.
• Where you went, at least well enough to identify the journey later.

Most authorities also want your odometer reading at the start and end of the year, so the business share can be sanity-checked against the total distance the vehicle covered. That is the number that makes a log defensible: it shows the business miles as a fraction of something real, not a figure floating on its own.

Check the specifics your own tax authority publishes before you file. The requirements are stable but not identical from country to country, and the per-mile or per-kilometer rate changes most years.

Write it down at the time

This is the part people skip and the part that matters most. A record made at or near the time of each trip carries weight. A record assembled in April from bank statements, calendar entries and memory does not, and some authorities say as much in plain language.

The practical consequence: whatever you use has to be usable in the ten seconds between switching the engine off and getting out of the car. A spreadsheet on a laptop at home is a valid log that you will not keep. That is why the odometer reading is such a good anchor — it is on the dashboard in front of you, at exactly the moment you need it.

Standard rate or actual expenses

Broadly, there are two ways to turn business driving into a deduction. You can multiply your business distance by a flat rate published by the tax authority, or you can claim the business share of what the vehicle actually cost you — fuel, insurance, servicing, depreciation.

Both routes need the same underlying record. The flat-rate method needs your business distance; the actual-cost method needs your business distance and your receipts, because the business share is a percentage of total mileage. Either way, a log with a distance and a purpose on every line is the thing you cannot skip.

Which one comes out ahead depends on the vehicle and the year, and in some jurisdictions choosing one in the first year constrains what you can do later. That is a question for your accountant, not for a landing page.

What this looks like in Odometer

Odometer was built around this specific job, which is why it does not try to detect trips for you:

• You type the start and end odometer readings; the distance calculates itself. No estimate, no GPS trace to argue about.
• One tap marks the trip business or personal, and a note field holds the purpose.
• Backdating is date-aware. Log a drive from last Tuesday and Odometer prefills the reading the vehicle actually had that day, and refuses entries that would make the mileage run backwards in time.
• At the end of the year, export a CSV with ISO dates and summaries for any date range, or a PDF report with the deduction worked out at the rate you set.
• Costs go in the same place, under fuel, tolls, parking, maintenance, car wash or other — so the actual-expenses route is available if that is the one you take.

The rate is a field you set, not a number we hardcode, precisely because it changes and because it is different everywhere. Put in whatever your tax authority publishes for the year you are filing.

The habit, not the app

Every mileage log that survives a review has one thing in common, and it is not the tool. It is that someone wrote the number down every time. Pick whatever makes that take five seconds — a notebook is fine — and then actually do it on the trips that are boring and short, which are the ones that add up.