Why Was So Much Tax Taken Off Your Commission?

Understanding Your Result

Withholding vs. Your Final Tax Bill

The number this calculator shows is what your employer deducts at source — not what you'll ultimately owe CRA. Those two figures are usually different.

Commission withholding runs high because payroll rules treat your payment as if it repeats every pay period. A $15,000 quarterly commission gets annualized to $60,000 of commission income on top of your salary — even if it was a one-time payment. Whatever was over-withheld comes back as a refund when you file your T1 in the spring.

Effective Rate vs. Marginal Rate

Your marginal rate is the highest rate applied to your last dollar of income. Your effective rate is the actual blended percentage across all your income — almost always lower. On commission income, the gap between these two numbers can be large.

• Marginal rate: reflects the top bracket your annualized income reaches — not the rate on your whole paycheque
• Effective rate: what you actually pay across all brackets, averaged over your full annual income
• Annualization temporarily pushes commission income into higher brackets, which is why the withholding percentage can look so much steeper than your effective rate

CPP1, CPP2, and EI

These three deductions are calculated separately from income tax. Your tax bracket does not affect them.

• CPP1 applies to earnings up to the first ceiling ($73,200 in 2026); maximum employee contribution is $4,230.45
• CPP2 applies between $73,200 and $81,900 — once your income crosses that threshold, CPP2 noticeably increases the total deduction on higher commission payments
• EI applies to insurable earnings up to $65,700; maximum employee premium is $1,123.07
• This calculator shows the employee side only — your employer's matching CPP and EI contributions are not included in your result

TD1X Impact

If you regularly spend on deductible employment expenses — vehicle use, home office, client costs — you can file a TD1X with your employer to reduce income tax withheld each period instead of waiting for a spring refund.

• TD1X reduces the income used to calculate income tax withholding; it does not reduce CPP or EI
• The calculator shows what withholding looks like with and without a TD1X on file — it does not confirm whether CRA will accept your specific expense claims
• Your actual deductible expenses still need to be supported when you file your T1

Why Your Result Looks Like This

The Annualization Effect

Payroll software doesn't know your commission is a one-time payment. It takes the amount, multiplies it by your pay frequency, adds that to your salary, and uses the combined total to determine your tax bracket for the period.

A $10,000 commission on top of a $70,000 salary can briefly make payroll calculate withholding as if you earn much more annually — so the tax on that single cheque reflects brackets your actual full-year income may never reach.

Why the Cheque Can Feel Over-Taxed

Withholding is designed to protect against underpayment at year-end. The system takes more now rather than leaving you with a balance owing in April.

If the annualized calculation put you in a higher bracket than your real annual income warrants, that excess comes back as a refund when you file your T1. The money isn't gone — it's held until you reconcile at tax time.

CPP2 Can Add a Noticeable Jump

Once your income crosses the CPP2 threshold ($73,200 in 2026), a second layer of CPP contributions starts applying on top of CPP1. For employees who hit that threshold during a strong commission month, the total CPP deduction can increase noticeably — even if it hasn't appeared on a paycheque before that point.

CPP2 continues until you reach the annual maximum. It doesn't reset mid-year and it isn't affected by your income tax bracket.

Why Two Similar Commissions Can Take Home Differently

Withholding is recalculated every pay period based on your situation at that moment. Two commissions of the same amount, paid at different points in the year, can produce different net cheques because of:

• Year-to-date income — earlier in the year, less has accumulated, which can shift annualized bracket calculations
• CPP and EI already paid — once you hit the annual maximums, those deductions stop for the remainder of the year
• Cheque size — a larger commission pushes annualized income higher and can tip the calculation into the next bracket
• Payroll timing — the number of remaining pay periods in the year affects how income is spread across the annualization formula

Why Commission Feels Over-Taxed at Source

Commission withholding feels aggressive because payroll rules force your employer to annualize the payment. They take your commission, multiply it by the number of pay periods per year, add the result to your annual salary, and use that total to determine your tax bracket. A $10,000 monthly commission on top of a $70,000 salary makes the CRA formula treat you as though you earn $190,000 — so the commission gets hit with the 29% federal bracket and 12.16% Ontario bracket even if you won't come close to that income for the year.

The result is almost always over-withholding at source. Any excess comes back when you file your T1 return in the spring. This calculator shows you the withholding on a single payment so you know exactly what to expect before the cheque lands.

If you regularly spend on deductible employment expenses — vehicle costs, home office, client meals, professional fees — filing Form TD1X with your employer lets them reduce the income tax withheld by those amounts. It doesn't change your annual tax bill. It moves cash back into your hands now instead of waiting for a spring refund. CPP and EI always apply to the full gross commission regardless.