The Capital Cost Allowance class for computers and computer equipment depends on when you purchased the equipment. Computers and computer equipment acquired after March 18, 2007 are in Capital Cost Allowance (CCA) class 50 with a Capital Cost Allowance rate of 55 percent. The computer equipment and/or systems software in question must not be used "principally as electronic process control, communications control, or monitor equipment" (Canada Revenue Agency).
Computers purchased between Jan. 27, 2009 and Feb. 1, 2011, are subject to a 100 percent capital cost allowance (CCA) rate. This means that you can deduct 100 percent of a computer purchase the year of purchase rather than simply deducting the amount that the computer has depreciated that year.
As for old equipment, computer equipment and/or systems software purchased after March 22, 2004 but before March 18, 2007 will be included in Capital Cost Allowance class 45 with a CCA rate of 45 percent.