Mortgage porting is the process of transferring your existing mortgage — including its rate, terms, and remaining balance — from your current home to a new one. If you're locked into a great low rate and don't want to trigger a costly prepayment penalty by breaking your mortgage, porting can save you thousands of dollars.
How Mortgage Porting Works
When you sell your home and buy another, you have two options: break your current mortgage (and pay a penalty) or port it to the new property. Porting keeps your existing rate and remaining term intact — you're essentially moving the mortgage, not ending it.
Porting When You Need More Money
If the new home costs more than your current mortgage balance, you'll need additional funds. Most lenders offer two approaches:
- Blend and increase: Your existing rate is blended with the lender's current rate on the additional amount, creating a new blended rate. The term may also extend.
- Two separate mortgages: Keep your existing mortgage as-is and add a second mortgage (or HELOC) for the additional amount at current rates.
Porting + Blend Example
You have $380,000 remaining at 2.89% with 3 years left. New home requires $520,000 total. You need $140,000 additional. Lender's current 3-year fixed rate is 4.59%.
Blended rate calculation: ($380,000 × 2.89% + $140,000 × 4.59%) ÷ $520,000 = 3.33% blended rate
This is significantly lower than taking a new $520,000 mortgage at 4.59% — saving you roughly $650/month.
Pros and Cons of Porting
Pros
- Avoid prepayment penalty (saves $5,000–$30,000+)
- Keep your existing low rate
- Same terms and amortization schedule
- Particularly valuable if you locked in below 3%
Cons
- Must re-qualify — not guaranteed
- Closing dates must align closely
- Not all mortgages are portable
- Additional funds blended at higher current rates
- Can be administratively complex
When Porting Is NOT Available
- Your mortgage isn't portable: Check your mortgage documents — portability is not guaranteed. Some lenders restrict porting on certain products (e.g., HELOC components).
- Closing dates don't align: If there's a gap longer than your lender's porting window (usually 30-90 days), porting may not be possible without a bridge loan.
- You don't re-qualify: If your income or the new property's value doesn't meet current underwriting standards, your lender can deny the port.
- The new property is ineligible: Lenders may restrict porting to owner-occupied properties. Porting to a rental or vacation property may not be permitted.
Is Porting Always the Best Option?
Not necessarily. Compare the math:
- Calculate the penalty to break your mortgage
- Calculate the interest savings from porting your lower rate vs. a new market rate for the remaining term
- If the penalty exceeds the interest savings from porting, breaking and getting a fresh rate might actually be financially equivalent or better
This calculation matters most when the rate difference between your existing rate and current market rates is small. If you locked in at 2.29% and current rates are 4.59%, porting almost always wins decisively.
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Get KOHO Free — Use Code 45ET55JSYAFrequently Asked Questions
No. Your amortization clock keeps running from the original start date. If you've been paying for 3 years on a 25-year amortization, you have 22 years left — porting doesn't reset this.
Yes, but the remaining mortgage balance must fit within the LTV (loan-to-value) limits of the new property. If the new home is worth significantly less, you may need to pay down a portion of the mortgage — which could trigger a partial penalty.
You'd need bridge financing for the gap period. Most lenders who allow porting provide bridge loans automatically. The cost is usually modest for a short bridge period.
Yes — you must re-qualify under the current stress test rules on the new property. This can be a barrier if your financial situation has changed or if the new property is more expensive.