Blog · August 5, 2026

Odometer readings, year bounds, and the percent-of-driving check

Why the CRA asks for start and end of year odometer readings, how two readings turn a log into a percentage, and a monthly habit that catches gaps early.

The logbook records the trips you claim. The odometer records every kilometre the car drove, claimed or not. The CRA wants both, and the reason is simple: without the second number, the first one cannot be turned into a percentage, and without a percentage there is no deduction. Here is why the year-bound readings matter, and how to use them during the year rather than only at the end.

What the CRA asks for

Alongside the trip records, the CRA asks for the odometer reading at the start and at the end of each fiscal period. For a calendar-year filer, that is January 1 and December 31. If you buy, sell or replace a vehicle during the year, record the reading on the day of the change too, so each vehicle has its own pair.

The two readings give the total kilometres for the year. Business kilometres from the log, divided by that total, is the business-use percentage. On T2125 that percentage is applied to the year’s actual vehicle costs. For an employee with a T2200 deducting expenses, the same arithmetic applies.

There is no special form. A dated note, a photo of the dash, or an entry in the app is enough, as long as it is dated and kept with the log.

The readings are also a sanity check

Two odometer readings do a second job that the CRA does not spell out but an auditor certainly performs: they bound the log.

If the odometer shows 24,000 km for the year and the log claims 25,000 business kilometres, the log is wrong. If the log claims 23,500 of 24,000, the driver is saying that almost every kilometre was business, including groceries and visits to family, and that will be questioned. A claim of 9,600 out of 24,000, or 40%, with a log that accounts for those 9,600, is the kind of number that passes without comment.

This works in the other direction too. If your log says 9,600 business kilometres and you know from experience that roughly half your driving is for work, an odometer total of 40,000 km tells you the log missed a lot of trips. The percentage is lower than reality, and the claim is smaller than it should be.

Percent of driving logged

That second case is worth turning into a habit. Take two readings some time apart, subtract to get the kilometres the car actually drove, and compare with the kilometres your log recorded in the same window, business and personal together. The ratio is the share of your driving that made it into the log.

Odometer on June 1: 41,200. Odometer on July 1: 43,350. The car drove 2,150 km.
Log for June: 1,980 km across all trips.
Logged share: 1,980 ÷ 2,150 = 92%.

A share in the low nineties is typical of an automatic tracker on a car that pairs reliably; the missing few percent are parking-lot repositions, short errands under the app’s minimum, and GPS shortening corners. A share of 60% means something is wrong: the app is not waking, a second driver uses the car, or you have been driving a vehicle the app does not know. A share over 100% means the log has duplicates, or a reading was entered wrong.

The point is that the number tells you in July, not in April of next year when your accountant asks.

A monthly check-in

A reading on the first of each month takes ten seconds and gives you eleven intermediate checkpoints between the two the CRA requires. It also gives you a record of the odometer for the month a trip might be disputed, and it makes a mid-year vehicle change painless because you already have a reading near the date.

Pair it with a glance at the logged share. If it drops, look at the log for that month and find out why while you still remember where you went. A missed week in June can be added from a calendar in July. The same week is a guess by next spring.

When the readings disagree with the log

Three common reasons, in order of likelihood:

Trips missed. The car drove with the app silent: force quit, phone left at home, a second driver, or a car that did not pair that day. Add the trips by hand if you can document them.
Trips duplicated or merged wrong. Two apps running at once, or a manual entry that duplicated an automatic one.
A typo in the reading. 43,350 entered as 45,350 adds 2,000 phantom kilometres. Photograph the dash when you enter a reading so you can check later.

If the readings are right and the log is short, the honest response is a lower business-use percentage, not an inflated log. The odometer is the hard number.

Year end

On December 31 (or the first morning of January before anyone drives), take the closing reading and photograph it. Enter it. Then export the year’s log with both readings on it and file the export with your tax papers. The next reading, on January 1, opens the new year. It is the same number, and it is worth entering twice so each year’s report stands on its own.

Odie keeps dated odometer readings, uses two of them to show what share of the car’s driving has been logged, and puts the year’s opening and closing readings in the PDF and CSV report next to the business-use percentage.

Sources

Written by the Odie team. Not tax advice; your accountant knows your situation.