Tax Deduction
A tax deduction reduces your taxable income before tax is calculated, effectively saving you money at your marginal tax rate. The higher your marginal rate, the more valuable a deduction becomes. This is why RRSP contributions are particularly valuable for high-income earners.
Common deductions include: RRSP contributions, union and professional dues, child care expenses, moving expenses (if you moved for work or school), carrying charges on investments, and the self-employed portion of CPP contributions. Business expenses for self-employed individuals are also deductible against business income.
The distinction between deductions and credits matters for tax planning. A $1,000 RRSP deduction at a 40% marginal rate saves $400 in tax. A $1,000 non-refundable tax credit (applied at the lowest federal rate, 14% in 2026) saves $140. This is why financial planners recommend contributing to an RRSP when your marginal rate is high and withdrawing when it's lower (typically in retirement).
How it works
A deduction is subtracted from your income before your tax bracket and rate are ever applied, which is why its value scales with your marginal tax rate rather than staying fixed like a non-refundable credit. The higher the bracket you're in, the more each dollar of deduction is worth to you.
Timing matters for deductions you control, like RRSP contributions: you can make the contribution in one year but delay claiming the deduction to a future year when your marginal rate is expected to be higher, since unused RRSP deduction room carries forward indefinitely. Self-employed individuals also deduct eligible business expenses directly against business income before the remainder is taxed as personal income.
A frequent mix-up is treating a deduction and a credit as interchangeable when comparing tax-saving strategies. They are calculated completely differently, and confusing the two can lead to overestimating how much a particular deduction or credit is actually worth to you at your specific income level.
Example: how a $1,000 deduction compares to a $1,000 credit
A $1,000 RRSP contribution is a deduction — it reduces your taxable income by $1,000 before tax is calculated. At a 40% marginal rate, that saves $1,000 x 40% = $400 in tax.
A $1,000 non-refundable tax credit works differently: it's applied at the lowest federal rate, 14% for 2026, so it only saves $1,000 x 14% = $140 in tax — regardless of your marginal rate.
This is why RRSP contributions, a deduction, are most valuable to someone in a high tax bracket now who expects a lower bracket in retirement, while credits deliver the same flat-dollar benefit to everyone who qualifies, no matter their income.
Frequently asked questions
Is an RRSP contribution a deduction or a credit?
It's a deduction — it reduces your taxable income before tax is calculated, rather than reducing your tax payable directly the way a credit does, which is why its value scales with your marginal tax rate.
Why are deductions worth more to high-income earners than to low-income earners?
Because a deduction's value equals your marginal tax rate multiplied by the deduction amount, and marginal rates rise with income — the same $1,000 RRSP deduction saves far more tax for someone in a high bracket than for someone in a low one.
Can I choose not to claim a deduction I'm entitled to this year?
For some deductions, like RRSP contributions, yes — you can make the contribution now but delay claiming the deduction to a future year when your marginal rate is expected to be higher, since unused RRSP deduction room carries forward indefinitely.
Related Terms
RRSP (Registered Retirement Savings Plan)
An RRSP is a government-registered account where contributions are tax-deductible and investments grow tax-free until withdrawal.
Marginal Tax Rate
The marginal tax rate is the rate of tax applied to your last (or next) dollar of income.
Tax Credit
A tax credit directly reduces your tax payable, dollar for dollar.