Can I claim rental expenses for the room for my business and my husband-for his? Both are working from home.

As per the CRA: If you and your spouse both worked from home

If you both meet the eligibility criteria, you must decide which expenses each of you will claim. Each expense can be claimed only once.

In order to determine the amount you can deduct, you have to first determine the eligible home office expenses you can claim and then calculate the total employment-use amount of those expenses.

Please read this carefully to know exactly what can be claimed and how much. 

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