Estimate how much tax an RRSP or FHSA deduction saves at your combined marginal rate, and what the contribution really costs you after tax.
An RRSP or FHSA contribution does not earn a refund on its own. It is a deduction: it lowers taxable income, and the tax saved is roughly the deduction multiplied by your combined marginal rate, as long as the whole deduction falls within one bracket.
Formula: tax saving ≈ deduction × marginal rate; after-tax cost = deduction − tax saving.
Worked example (illustrative, Ontario, 2026): with taxable income of about $74,273, the combined marginal rate is 20.5% federal + 9.15% Ontario = 29.65%. A $5,000 deduction saves about $5,000 × 29.65% = $1,482.50, so the contribution costs $3,517.50 after tax. In this particular case the deduction also drops income below $72,000, which reduces the Ontario Health Premium by $150, so the real saving is $1,632.50. The RRSP refund guide shows the full working.
Find your marginal rate with the marginal vs average rate guide. If a large deduction crosses a bracket threshold, split it: part at the higher rate, part at the lower one.
Limits: RRSP withdrawals are taxed later, so the saving is a deferral, not a gift. Income-tested benefits (CCB, the Canada Groceries and Essentials Benefit, OAS recovery) can make the real effect larger. You must have contribution room; check it in CRA My Account. General information only.
Worked Calculations and Checklists
CCB maximums for July 2026 to June 2027 ($8,157 under 6, $6,883 aged 6 to 17), the income thresholds and reduction rates, worked examples and how RRSP deductions raise it.
Worked Calculations and Checklists
How the FHSA works for 2026: $8,000 a year and $40,000 lifetime, carry-forward room, the deduction worked out, qualifying withdrawals, combining with the HBP and pitfalls.
Worked Calculations and Checklists
The difference between your marginal and average tax rate, 2026 Ontario combined marginal rates by income, benefit clawbacks, and which rate to use for RRSPs, raises and gains.
Worked Calculations and Checklists
How your 2026 RRSP deduction limit is calculated ($33,810 cap), the March 1, 2027 deadline, a worked refund calculation, and when delaying the deduction pays off.
