CRA simplified logbook: 12-month base year plus 3-month sample
How to keep a CRA-compliant logbook without logging every trip every year.
The simplified method explained
The CRA recognises that asking sole proprietors and employees to log every business kilometre forever is heavy.[^cra-logbook-86] Their compromise: keep a **12-month base-year logbook** with every trip, then in subsequent years keep a **3-month representative sample** and extrapolate to the full year, provided the pattern is consistent (within 10% of the base year).
Year 1: the full base-year logbook
For the first 12 consecutive months of business use of a vehicle (not necessarily a calendar year), record every business trip with:
- Date - Destination - Purpose (business reason) - Kilometres
Also record total kilometres on the odometer at the start and end of the period to compute the business-use percentage:
**Business-use % = (Sum of business km) / (Total km in the period)**
This ratio becomes the baseline.
Year 2 onwards: the 3-month sample
In each subsequent year, log every business trip for **a representative 3-month period** (CRA suggests using the same calendar quarter as in the base year for stability). Compute the sample's business-use % and apply this consistency check:
**| Sample % − Base-year same-quarter % | ≤ 10 percentage points**
If the difference is within 10 pp, you can extrapolate the sample's business-use % to the full year and deduct expenses on that basis. If outside 10 pp, you fall back to the full-year logbook.
Worked example
Base year (2024): - Q3 business-use %: 65%. - Full-year business-use %: 67%.
2026 sample (Q3): - Business-use %: 70%.
Check: |70% − 65%| = 5 pp → within 10 pp, so the sample is consistent. Apply 70% × (67% / 65%) = ~72.2% as the inferred 2026 full-year business-use %.
This 72.2% is then applied to total expenses (fuel, insurance, lease, maintenance, CCA) to compute the deductible portion.
What CRA expects in an audit
- The full base-year logbook with every trip. - The annual sample logbook(s) with every trip in the sample period. - Odometer readings for the start and end of the base year and each sample period. - A spreadsheet or system showing the consistency check and extrapolation.
Tools that help
Manual paper logs are accepted but rarely defensible at audit. GPS-based digital tools — like Quilometragem — capture each trip with date, distance, route, business purpose and a tamper-evident hash, eliminating both data-entry error and integrity questions.
When to switch back to full-year logging
- Major change in role (new territory, change from inside sales to outside sales). - Major change in vehicle (much higher or lower mileage profile). - A failed consistency check (gap > 10 pp).
After a 12-month full logbook is reset, the simplified method can resume.
Bottom line
The simplified method is one of the few CRA accommodations that genuinely reduces compliance burden without sacrificing audit defence. Use it: one full base year, then 3-month samples thereafter. Total annual logging effort drops by ~75% with no loss of deduction.