Portable Mortgages: Could You Take Your Rate With You?

Twenty percent of outstanding American mortgages carry a rate below 3%. New loans are pricing above 6%. That gap is the single biggest reason the housing market is stuck — not affordability in the abstract, but the fact that selling means giving up a rate you will never see again.

A portable mortgage is the obvious fix. You move, and the loan moves with you. It’s ordinary in the UK and Canada, the FHFA says it’s evaluating it, and there’s a bill in Congress. There’s also a reason it has never existed here, and it isn’t a lack of imagination.

What Portability Actually Means

You sell your house and buy another. Normally the sale pays off your existing mortgage and you originate a new one at whatever rates are that week. With portability, the loan — rate, balance, remaining term — detaches from the old property and reattaches to the new one.

Say you owe $310,000 at 3.25% with 26 years left, and you’re buying a house that needs a $390,000 loan. In a portable system you’d carry the $310,000 at 3.25% and borrow the extra $80,000 at today’s rate, giving you a blended cost of about 3.95% instead of 6.66% on the whole balance. Keeping both pieces on a 26-year term, that’s $2,013 a month against $2,633 for a fresh $390,000 loan at market — a saving of roughly $620 a month.

That is a genuinely large number, and it explains the search volume. It also explains why the idea keeps resurfacing every time rates rise.

The Problem It’s Meant to Solve

The FHFA has quantified the lock-in effect in its own research, and the findings are stark. Every percentage point by which market rates exceed a homeowner’s existing rate cuts the probability they sell by 18.1%. Between the second quarter of 2022 and the second quarter of 2024, lock-in prevented an estimated 1.72 million transactions and pushed home prices up 7%.

Read that last part again. Lock-in doesn’t just stop people moving — it makes housing more expensive, because the homes that would normally come to market don’t. The average rate across all outstanding mortgages is around 4.4%; a new loan costs well over six. Millions of households are sitting on an asset they can’t sell without taking a large, permanent pay cut on their monthly budget.

Why It Doesn’t Exist Here: the Bond Market

Here’s the part most coverage skips, and it’s the whole reason this is hard.

American mortgages aren’t held by the bank that wrote them. They’re pooled into mortgage-backed securities and sold to investors, and those securities are priced on assumptions about how fast the loans in them will be repaid. People move roughly every seven to ten years, and when they sell, the mortgage is paid off. That prepayment is baked into what an investor pays for the bond.

Portability removes it. If borrowers carry their loans from house to house, the loans stop prepaying, and a security everyone priced as a seven-year instrument turns into a thirty-year one. The bond market calls that extension risk, and it is exactly the risk investors least want — you’re stuck holding a below-market rate for decades precisely when rates have risen.

So this is not a guideline change. It reaches into how securities are structured, how servicing contracts are written, and how loans are underwritten. It is a structural change to the plumbing of American mortgage finance, which is why an idea that sounds like common sense has sat unbuilt for forty years.

The Catch Nobody Mentions: Someone Pays for Your Rate

Suppose the structural problem gets solved. The below-market rate you keep doesn’t come from nowhere. Somebody is receiving 3.25% on money that’s worth 6.66% in the market, and that somebody is the investor holding your loan.

Investors who expect that will demand more yield up front to compensate for extension risk. More yield on the security means higher rates on new mortgages. Which means portability would hand a large benefit to people who already own a home with a cheap loan, and charge part of the cost to people buying their first one.

That may still be worth doing — unlocking 1.7 million transactions and easing supply would help first-time buyers through a different channel. But it isn’t free, and any version of this that gets described as costless is being sold to you.

How It Works Where It Actually Exists

Portability in the UK and Canada is more conditional than the American conversation implies. Three rules travel with it in both markets, and they’d almost certainly travel here too.

You requalify. Portability moves the rate, not the approval — income, credit and the new property all get underwritten again, and people who changed jobs or took on debt get turned down. You blend for anything extra: the old balance keeps the old rate, new money prices at today’s, and lenders quote you the weighted average. And it’s time-limited — typically you have somewhere between 30 and 120 days between the sale and the purchase, after which the rate is gone.

Buying somewhere cheaper is its own trap. Port a $310,000 loan into a house that only supports $240,000 and you may face a prepayment charge on the difference, which is the opposite of what a downsizing retiree expects.

Where It Stands

Two things are live. The FHFA said in January 2026 that it was evaluating how to offer portable and assumable mortgages at Fannie Mae and Freddie Mac in a safe and sound manner — the same statement in which Director Bill Pulte stepped back from the 50-year mortgage. Separately, Representative Tom Kean Jr. introduced the Making Ownership Viable for Everyone Act, which would require the enterprises to purchase portable loans.

Neither amounts to a product. An introduced bill is not a law, an evaluation is not a proposed rule, and neither addresses the securities problem underneath. If you want a signal worth watching, it’s the FHFA publishing an actual notice of proposed rulemaking, or the enterprises updating their seller guides. Until one of those happens, this is a policy conversation, not a mortgage you can apply for.

What You Can Actually Do Today

If your problem is that moving means losing a cheap rate, the tool that exists right now is the assumable mortgage — and it works the other way round. Portability moves the rate with the borrower; assumption leaves the rate with the house, so a buyer takes over the seller’s loan.FHA, VA and USDA loans are generally assumable, which means a seller holding a 2019 VA loan at 3.25% has something genuinely valuable to market.

The catch is the gap. If the house is worth $500,000 and the assumable loan balance is $280,000, the buyer needs $220,000 in cash or a second lien to bridge it, which rules out most people. It’s a real option in a narrow set of cases rather than a general answer.

And if you’re weighing whether to move at all: run the actual numbers rather than the rate headline. The rate you’d lose matters less than the balance you’d be refinancing and how long you plan to stay.