What you can actually claim
Most missed money isn't exotic. It's a receipt nobody kept, a credit claimed on the wrong spouse's return, or an amount that should have been carried forward to a year it was worth more.
Worth your marginal rate. $1,000 deducted at 43% saves about $430. RRSP, childcare, moving, union dues, employment expenses.
Calculated at the lowest rate — 14% federally in 2026 — and can only reduce tax to zero. Medical, tuition, donations, disability.
Arrives even with no tax owing — which is why filing at zero income still pays. GST/HST credit, CCB, Ontario Trillium Benefit.
The claims worth checking every year
Ontario-specific amounts
Bundles the Ontario Energy and Property Tax Credit, the Northern Ontario Energy Credit and the Ontario Sales Tax Credit into a monthly payment. Rent and property tax paid feed the calculation, claimed on the ON-BEN form. Refundable, and worth filing for even at low income.
Reduces or eliminates Ontario tax for lower-income workers. Calculated automatically from your return — nothing to claim, but another reason not to skip filing.
Paid alongside the federal Canada Child Benefit for lower and moderate income families, recalculated each July from the prior year's return.
Discontinued for tuition paid after early September 2017 — the federal credit still exists, the Ontario one does not. Older unused Ontario amounts carried forward can still be applied.
Three habits that recover real money
Medical, donations, childcare, the spousal amount and pension splitting all have a right-hand and wrong-hand answer. Preparing both returns side by side is where the saving is.
Donations carry forward five years, tuition indefinitely, student loan interest five years, RRSP deductions indefinitely. A claim made in a 14% year and a 43% year are not the same claim.
You can generally adjust the previous 10 years. A newly approved disability certificate, missed medical expenses, or an unclaimed spousal amount can all be recovered retroactively with interest.
Twelve questions that surface the claims most people forget — then bring the list to a review with a CPA.