Can i use interest paid on mortgage of promary residence if one room is used for home office

[TurboTaxKim]

If you are Self-Employed, you may be able to claim a portion of your mortgage interest if you use that space 

as your principal place of business, or only to earn your business income.

Here's some more information about claiming Business Use of Home expenses: 

• TurboTax Tip:  Your Small Business & Business-Use-Of-Home Expenses
• CRA Guide: Business Use Of Home Expenses 

If you are an employee and required to work from home, mortgage interest is not an allowable expense for commissioned or salaried employees.