CMHC default insurance is mandatory when your down payment is under 20%. The premium scales with Loan-to-Value (LTV) in 5 sharp tiers — and an extra 0.01% past a boundary can cost you thousands. See the cliff chart below.
Notice the jump: 80.00% LTV is 2.40%, but 80.01% LTV is 2.80%. Same loan size, $400 more in premium per $100k borrowed. Knowing the tier matters more than the rate alone.