You can claim work from home benefit for the past and current year. The amount you can claim for work-space-in-the-home expenses is limited to the amount of employment income that is left after you have deducted all other employment expenses. This means that you cannot use work-space-in-the-home expenses to create or increase a loss from employment. If you cannot claim all your work-space-in-the-home expenses in the year, you can carry forward the expenses. You can claim these expenses in the next year as long as you are reporting income from the same employer. However, you cannot create or increase a loss from employment by carrying forward work-space-in-the-home expenses. 

For further information, please see the links below:

Canada Revenue Agency Q&A: Frequently asked questions – Home office expenses for employees 

TurboTax FAQ/video: Home Office Deductions for Self-Employed and Employed Taxpayers

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