The calculator below will give you an idea of how much CMHC insurance might cost on your mortgage. Put in an asking price and a down payment amount and it will estimate your mortgage insurance premium. Mortgage default insurance, also referred to as CMHC insurance, is mandatory in Canada for down payments of less than 20% of the purchase price. Mortgage default insurance protects lenders in the event a borrower stops making payments and defaults on their mortgage loan. CMHC insurance premiums are paid for in full by the borrower at the start of their mortgage.