According to the Canada Revenue Agency, taxable income is the amount used to calculate federal tax and provincial or territorial tax on the income tax return. Taxable income is calculated by subtracting tax deductions from total income. Total income is the sum of income from all sources, such as employment, business, investment, pension, and other income. Tax deductions are amounts that can be subtracted from total income to reduce the amount of income that is subject to tax. Some examples of tax deductions are RRSP contributions, child care expenses, moving expenses, and alimony payments. Tax credits are not subtracted from total income, but rather from the tax payable. Tax credits are amounts that can reduce the amount of tax owed or increase the amount of refund. Some examples of tax credits are basic personal amount, spouse or common-law partner amount, Canada workers benefit, and foreign tax credit.

Therefore, the correct answer is C. total income less tax deductions.

References: 1: Line 26000 – Taxable income - Canada.ca 2