Do you enter monthly home expenses if you're self employed or the total annual expenditure?

Annual. If you use part of your home for both your business and personal living, calculate how many hours in the day you use the rooms for your business, and then divide that amount by 24 hours. Multiply the result by the business part of your total home expenses. This will give you the household cost you can deduct. If you run the business for only part of the week or year, reduce your claim accordingly.

To help calculate your business-use-of-home expenses, complete the "Calculation of business-use-of-home expenses" on Form T2125, Part 7. For an example of the calculation of these expenses, go to Calculating Business Use of Home Expenses. The expenses you claim cannot have been claimed elsewhere on Form T2125.