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A tax deduction is an amount subtracted from your income before tax is worked out, so it reduces the income being taxed rather than the tax bill directly. Its worth depends on your marginal rate: the higher the rate, the more the deduction saves. Common examples are RRSP contributions, child care costs, union dues, moving expenses and business expenses. Credits work the other way, reducing the tax calculated on that income.

Tax exempt describes an amount or a transaction that tax does not apply to at all, which is different from a deduction or credit that merely reduces tax. Common examples are supplies that are exempt or zero-rated for GST/HST, investment income earned inside a TFSA, and specific receipts Parliament has excluded from income. Registered charities and non-profits can be exempt from income tax while still carrying filing duties. Exemption is never automatic; the rule must fit your facts.

A write-off is simply a deductible expense. You subtract it from the income it helped earn, so the saving equals the expense multiplied by your marginal tax rate, not the full amount spent. To qualify, the cost must be incurred to earn business or employment income, be reasonable in amount, and be backed by a receipt. Purely personal costs never qualify, and mixed-use items such as a vehicle or a home office are split by business-use proportion.

Some of them, yes. Where your income is too low to use them, specific non-refundable credits may be transferred to a spouse or common-law partner, including the age amount, the pension income amount, the disability amount and part of tuition. The transfer is limited to the portion you cannot use yourself, and your partner claims it on their own return. The basic personal amount is not transferable, and Canada has no general marriage allowance transfer.