Prime Rate Explained: What Happens to Your Payment If Prime Hits 4.70%

Rate mechanics, September 25, 2026. The prime rate at most Canadian lenders is 4.45%, sitting roughly 220 basis points above the Bank of Canada's 2.25% policy rate. The market-implied path has it at 4.70% by the end of 2026 and 5.70% in 2027. On a $500,000 variable rate mortgage at prime minus 1.10%, that first 25-basis-point step costs you $65.89 more a month; the full move to 5.70% costs $338.30 a month, or $4,059.60 a year.

Below is the mechanical version of how the prime rate affects your mortgage: who sets it, how the prime-minus discount works, and why the hit to your household is bigger than the mortgage number alone.

What the prime rate is, and who sets it

The prime rate is the posted reference rate each lender uses to price its floating-rate products. It is not set by the Bank of Canada. Every bank, credit union and monoline publishes its own and decides when to change it.

In practice they move almost in lockstep. When the Bank of Canada changes the overnight rate, lenders follow with a matching change — but not on announcement day and not automatically. The pattern is an announcement within hours or a day, effective a few business days later. So if the Bank hikes 25 basis points on Wednesday, October 28, 2026 at 9:45 a.m. ET, expect prime to move to 4.70% within days, not minutes.

Three details matter for your file:

• Lenders can pass through less than the full change. Nothing forces a one-for-one match.
• The effective date is the lender's. Your payment adjusts on the first scheduled payment after it, which can push the increase into the following month.
• Your lender's prime is the one in your commitment. If you are with a monoline posting a different number than the big six, check your own statement first.

Prime minus: your discount is locked, prime is not

Variable mortgages are quoted as a spread to prime. The best five-year offers sit around 3.35% to 3.49% — prime minus 1.10% to prime minus 0.96%. That discount is contractual: sign at prime minus 1.10% and the 1.10% is yours for the full term. Prime is the part that floats:

• Prime 4.45% minus 1.10% = 3.35% (today)
• Prime 4.70% minus 1.10% = 3.60% (implied end-2026)
• Prime 5.70% minus 1.10% = 4.60% (implied 2027)

This is the part borrowers get wrong at renewal. A deep discount does not protect you from a hike; it only means your rate starts lower. A 25-basis-point move in prime is a 25-basis-point move in your contract rate whether your discount is 0.96% or 1.10%. The spread is worth something only relative to what a new borrower could get today, which is why negotiating it at the outset matters more than where prime sits on signing day. On the locked-versus-floating decision itself, see Variable or Fixed in Late 2026.

What happens to your payment when prime hits 4.70%, then 5.70%

The table runs a 3.35% variable (prime minus 1.10%) on a 25-year amortization at three balances. Payments use the Canadian semi-annual compounding convention, which is how your lender calculates them.

Mortgage balance	Prime 4.45% (rate 3.35%)	Prime 4.70% (rate 3.60%)	+$ per month	Prime 5.70% (rate 4.60%)	+$ per month vs today
$300,000	$1,474.16	$1,513.69	+$39.53	$1,677.14	+$202.98
$500,000	$2,456.93	$2,522.81	+$65.89	$2,795.23	+$338.30
$750,000	$3,685.39	$3,784.22	+$98.83	$4,192.84	+$507.45

Read it in two steps, because that is how it arrives. The first is small: $39.53 a month on $300,000, $65.89 on $500,000, $98.83 on $750,000. Nobody reorganises a budget over $66.

The 2027 scenario is the one that bites. Going from 4.45% to 5.70% adds $2,435.76 a year on $300,000, $4,059.60 on $500,000 and $6,089.40 on $750,000. And it does not land as one shock — it comes as four or five quiet 25-basis-point steps, each easy to absorb, which is why the cumulative total catches people out.

The mortgage is not the whole bill

Prime prices far more than your mortgage, so a prime rate increase hits every floating balance you carry at once:

• HELOCs — your HELOC rate is typically prime plus roughly half a point, floating, with no fixed-payment option.
• Unsecured lines of credit — prime plus a wider spread, often several points.
• Some student lines and car loans — floating student lines sit at or just above prime, and variable auto financing moves too.
• Business operating lines — if you are self-employed, these reprice too.

Below is a household carrying a $500,000 variable at prime minus 1.10% plus a $100,000 HELOC, shown as a worked example priced at prime flat and paid interest-only. Most HELOCs sit above prime, so treat it as the floor.

Scenario	Mortgage payment ($500,000 at prime −1.10%)	HELOC interest ($100,000 at prime)	Combined monthly	Increase vs today
Prime 4.45% (today)	$2,456.93	$370.83	$2,827.76	—
Prime 4.70% (+25 bps)	$2,522.81	$391.67	$2,914.48	+$86.72
Prime 5.70% (+125 bps)	$2,795.23	$475.00	$3,270.23	+$442.47

The mortgage is $338.30 of that $442.47; the HELOC adds $104.17. Annualised, the household is out $5,309.60 — about 31% more than the mortgage-only figure most people run in their heads. If the HELOC is doing the damage, compare structures in Second Mortgage vs HELOC in Canada.

ARM vs VRM: does your payment move, or your amortization?

Two variable mortgages at the same rate behave very differently when prime moves, and most borrowers do not know which they signed.

Adjustable-rate (ARM)

Your payment is recalculated after each prime change. The table figures above are ARM figures. You feel the increase in cash flow immediately, your amortization stays on schedule, and nothing accumulates out of sight.

Static-payment variable (VRM)

Your payment stays the same dollar amount. When prime rises, more of it goes to interest and less to principal, and the amortization quietly stretches. On a $500,000 balance with the payment fixed at $2,456.93, a move to a 3.60% contract rate pushes remaining amortization from 25 years to roughly 26.1 years. At 4.60% it stretches to about 32.6 years. Cash flow never changes; you just pay for seven more years.

Push far enough and you reach the trigger rate — the contract rate at which your fixed payment no longer covers the month's interest. On that same balance at $2,456.93 it sits near 5.97%, requiring prime around 7.07%: about 262 basis points above today's rate, well beyond the implied path. Not the live risk this cycle, but static-payment borrowers should know the number.

Call your lender and ask one question: if prime goes up 25 basis points, does my payment change? The answer decides whether you find $66 a month or quietly add a year to your amortization.

The implied path is a market expectation, not a forecast

The 4.70% and 5.70% figures come from bond and swap market pricing, not anyone's published outlook. As of September 30, 2026 markets put a 54% probability on a 25-basis-point hike at the October 28 decision — other outlets published a range of roughly 38% to 60% in late September as odds moved quickly — and effectively a 100% probability by December 9.

Most bank economists are more dovish. RBC and Scotiabank both see 2.50% by end-2026, matching the market's first step. But CIBC, National Bank, Desjardins, Capital Economics, TD, BMO and Oxford Economics all have the Bank holding at 2.25% through 2026. That gap matters: if the economists are right, the prime rate Canada's lenders post stays at 4.45% and the column to plan around is the first one.

The case for a hold is in the data — August payrolls fell 42,000 against an expected 15,000 gain, unemployment held at 6.4%, wage growth dropped to 2.0% (slowest in four years) and July real GDP was flat. The case for a hike is headline inflation stuck at 3.0%, driven largely by gasoline at +23% year over year, though core sits at 2.0%, right at target. The October 19 CPI release lands nine days before the decision.

Fixed rates run on a different mechanism entirely — Government of Canada bond yields, not prime — which is why five-year fixed has already moved up roughly half a point while the policy rate has not budged; the full explanation is in Rate Alert: Fixed Mortgage Rates Are Rising.

Common questions

What is the prime rate in Canada right now?

Prime sits at 4.45% at most Canadian lenders as of late September 2026, roughly 220 basis points above the Bank of Canada's 2.25% policy rate, which has been unchanged since October 2025 across seven decisions. Lenders post their own prime, so confirm the number on your statement.

How fast does prime change after a Bank of Canada decision?

Usually within days, not immediately. Lenders are not obliged to move on announcement day; the pattern is an announcement within hours or a day of the decision, with an effective date a few business days out. Your payment adjusts on the first scheduled payment after that date, which can push the change into the following month.

What is a trigger rate?

It applies only to static-payment variable mortgages. The trigger rate is the contract rate at which your fixed payment stops covering that month's interest, so the balance grows instead of shrinking. On a $500,000 balance with a $2,456.93 payment, it arrives near a 5.97% contract rate. Lenders typically contact you first and require a payment increase, a lump sum, or a switch to fixed.

What to do in the next four weeks

The decision lands October 28. Four things are worth doing before it:

• Find your discount and your structure: your spread to prime, and whether your payment is adjustable or static.
• Stress the 5.70% column, not the 4.70% one. If the 2027 scenario breaks your budget you have 12 to 18 months of warning — plan now rather than react later.
• Total every floating balance — mortgage, HELOC, unsecured line, operating line. Add 125 basis points to all of them and look at one number.
• If you are renewing inside 120 days, get a rate hold. It costs nothing and covers you against both a prime rate increase and further movement in fixed pricing. The October 28 decision is the near-term catalyst.

And do not take one lender's variable spread as the market. The gap between prime minus 0.96% and prime minus 1.10% is 14 basis points — on $500,000, about $37 a month, locked for five years, for no reason other than which lender you walked into. RateShop.ca is Canada's independent mortgage shopping and comparison marketplace: we compare A lender, B lender and private options side by side, so you see the whole market rather than one desk's offer. Bring your commitment and we will tell you what your spread is worth.