Thank you for your question,
As per CRA, when you rent only part of a building where you live, such as a room in your house, you can claim only the expenses that relate specifically to the rented part of the building. This means that you have to divide generic expenses for the property on a reasonable basis, such as the percentage of the total living area that is being rented. You also have to divide the expenses in line with the proportion of time the room is rented.
As a result, you cannot put the full receipt amount as your rental expenses if you rent only the part of a building. You can claim only a percentage if it is for part of your principal residence.
You can watch the video Claiming Expenses on Rental Properties to get more information.