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What less than 20% down really costs.
The CMHC premium, the tax you pay in cash at closing, and what the insurance costs over the life of the mortgage — plus what a bigger down payment would save.
What the quick estimates leave out
Four things that change the answer.
The 10% cliff
On an $800,000 home, 10% down is $80,000 and the premium is 3.10%: $22,320. Put down $79,200 — 9.9% — and the rate jumps to 4.00% on a slightly larger loan: $28,832. Eight hundred dollars less down costs $6,512 more. The premium steps down at 10%, 15% and 20% down, and the worst place to sit is just above a step.
Tax you pay in cash
The premium is added to your mortgage, but Ontario's 8% sales tax on it cannot be. On that $22,320 premium it is $1,785.60, due at closing on top of land transfer tax and legal fees. Most closing-cost estimates leave it out.
You pay interest on the premium
Because the premium joins your balance, it earns interest for as long as the mortgage runs. At 4.49% over 25 years, that $22,320 premium costs about $37,000 in total. The calculator shows the real number for your purchase.
A longer amortization costs more up front
Since December 2024, first-time buyers and buyers of new construction can insure a 30-year amortization. It lowers the payment, and it adds 0.20% to the premium rate on top of the extra interest.
Straight answers
Questions people ask about this.
What is CMHC insurance, and who does it protect?
Mortgage default insurance protects the lender if you stop making payments — not you. It is required when your down payment is under 20% of the purchase price, and you pay the premium. CMHC, Sagen and Canada Guaranty are the three insurers; this calculator uses CMHC's published rates.
How is the premium calculated?
It is a percentage of the mortgage before insurance, set by the loan-to-value ratio. With 5% to just under 10% down it is 4.00%; 10% to under 15% down, 3.10%; 15% to under 20% down, 2.80%. At 20% or more there is no premium. The percentage is added to your mortgage, so you never write a cheque for it.
Why does 9.9% down cost so much more than 10%?
Because the premium rate is set by which band your loan falls into, not by a smooth formula. Cross from 90.1% loan-to-value to 90% and the rate falls from 4.00% to 3.10% on the whole loan. The ladder table under the calculator shows every step for your price.
Do I pay sales tax on the premium?
In Ontario, yes — 8% provincial sales tax on the premium, and CMHC is clear that it cannot be added to the loan. It is cash due at closing.
Does the insurance stop when I reach 20% equity?
No. It is a one-time premium that becomes part of your mortgage balance at the start. It does not end, and it is not refunded, when your equity passes 20%.
How much do I need to put down?
5% of the first $500,000, plus 10% of the portion from $500,000 to $1.5 million. On a $900,000 home that is $25,000 plus $40,000: $65,000, or 7.2%. From $1.5 million up, you need 20% and the mortgage cannot be insured.
Who can use a 30-year amortization with less than 20% down?
Since December 15, 2024, first-time buyers and buyers of new construction. Everyone else is limited to 25 years on an insured mortgage. The longer amortization adds 0.20% to the premium rate.
What is a borrowed, or non-traditional, down payment?
A down payment that comes from borrowed money — a personal loan or line of credit — rather than savings, a gift or the sale of another asset. At 5% to just under 10% down, CMHC charges 4.50% instead of 4.00%.
Can you run this on a specific home?
Yes. Send me the address and I will model the purchase — premium, closing cash, and what the home is likely to need in its first years. I am a REALTOR®, not a mortgage professional, so the mortgage itself and your approval come from a licensed lender or broker; I will happily work alongside whoever you choose.