What We Built and Why
Most tax calculators in Canada show you your annual take-home pay. That's useful — but it doesn't help you make decisions. When you're deciding whether to take on freelance work, accept a bonus, make an RRSP contribution, or withdraw from a registered account, the question isn't "what's my average rate?" It's "what rate will I pay on this specific amount of additional income?"
That's the marginal rate. And it's surprisingly hard to find — not because it's secret, but because it requires combining federal brackets, Ontario provincial brackets, the Ontario surtax, CPP, EI, and OHP all at once, at a specific income point. We built ontariomarginaltaxcalc.ca to do exactly that, accurately, for Ontario residents in 2026.
Data Sources
All rates and thresholds are sourced from official Canadian government publications:
- CRA T4032-ON (Payroll Deductions Tables — Ontario, 2026): federal and Ontario income tax brackets, Basic Personal Amounts
- ESDC Employment Insurance Regulations: 2026 EI rate (1.63%), MIE ($68,900)
- CRA CPP Rate Notice (2026): CPP1 rate (5.95%), YMPE ($74,600), CPP2 rate (4.00%), YAMPE ($85,000)
- Ontario Ministry of Finance: Ontario Health Premium tiered schedule
- Ontario Taxation Act: Ontario surtax thresholds and rates
Calculation Methodology
The calculator uses an incremental difference method:
- Compute total tax (income tax + CPP + EI + OHP) at current income
- Compute total tax at current + additional income
- Divide the difference by the additional income amount
This is the same approach used by CRA's bonus withholding method (Method 2 per T4130), and it captures the actual blended marginal rate across bracket transitions — not just the rate at a single point. The Ontario surtax, which is a non-linear function of Ontario basic tax, is computed correctly for both income levels before subtracting.
Accuracy and Limitations
This calculator is designed for employment income for Ontario residents. It does not model self-employment double CPP, Quebec abatement, capital gains inclusion rates, eligible dividend gross-up, or personal credits beyond the Basic Personal Amount. For a definitive tax calculation, use CRA-certified tax software or consult a Chartered Professional Accountant (CPA).
Updates
Rates are updated annually when CRA publishes the T4032-ON and ESDC releases EI and CPP parameters. The current build reflects 2026 rates as confirmed at publication time.