Losses From an Office, Employment,
Business or Property, and ABILs - Amount Used in the Loss Year
1. When calculating income for a particular taxation year in accordance with section 3 of the Income Tax Act, a taxpayer can deduct (subject to certain limitations as described in 2 to 5 below)
•losses from an office, employment, business or property, and
•allowable business investment losses
incurred in the year,
against all types of income for the year. An allowable business investment loss (ABIL) is the allowable portion (for tax purposes) of a special type of capital loss. For a detailed explanation of the nature and calculation of an ABIL, see the current version of IT-484, Business Investment Losses.
Any reference in this bulletin to the "loss year" means the taxation year in which the particular loss was incurred.
http://www.cra-arc.gc.ca/E/pub/tp/it232r3/it232r3-e.html#2