Offset mortgages are often misunderstood and sometimes overlooked, but for the right borrower they're one of the most powerful tools available. Rather than earning savings interest separately, you use your savings to reduce the amount your mortgage interest is calculated on. The result is often a much larger saving than you'd get from even a top-rate savings account, especially if you pay higher rate tax.
How the interest saving works Let's say you have a £200,000 mortgage and £30,000 in savings. With an offset mortgage, your lender charges interest on £170,000 instead of £200,000. At a 4.5% rate, that's saving you roughly £1,350 per year in interest. And unlike savings interest, this saving isn't taxable. You still have full access to your savings at any time, so there's no lockaway risk. The catch is that offset mortgage rates tend to be slightly higher than standard deals, so it only works out better when your savings are substantial enough to make up the difference.
Paying off your mortgage faster One of the biggest benefits of an offset mortgage is the option to use your savings to shorten your term rather than reduce your payment. If you keep paying the same amount each month but your interest is worked out on a lower balance, more of each payment goes straight to the capital. Over a 25-year mortgage, even modest savings could cut several years off the term. Run both scenarios in the calculator: compare keeping your monthly payment the same versus reducing it, and see which approach delivers the better outcome for your situation.
Who benefits most from offsetting Offset mortgages work best for people with consistently high savings balances who pay income tax at 40% or above. The higher your tax rate, the less your savings earn after tax from a conventional account, making the offset route comparatively more attractive. They're also useful for self-employed people who hold large sums in their accounts throughout the year, and for families where parents want to link their savings to a child's mortgage without gifting the money outright. If you're unsure whether an offset mortgage is the right product for your circumstances, our advisers, fee-free on mortgages over £100,000, can compare the whole market and run the numbers with you.
Offset mortgage guide
An offset mortgage links your savings to your mortgage. Instead of earning savings interest, your savings balance is taken off your outstanding balance before the lender works out your interest charge. The offset mortgage calculator above shows what that could be worth to you. This guide explains how the offset benefit is worked out, when offset vs savings comes out on top, and the questions I ask clients before recommending an offset deal.
You keep your cash savings in an offset savings account with the same lender, sometimes alongside a current account. Each day, the lender takes the total of those credit balances away from your mortgage debt and only charges interest on what is left. Interest is usually calculated daily and applied monthly.
On a £200,000 mortgage with £30,000 in a linked savings account, you pay interest on £170,000. Your savings are still yours, and you can usually withdraw money whenever you like.
There are two different ways to use the offset benefit. You can keep your monthly mortgage payments the same, so more of each payment goes to capital repayment and you pay off your mortgage sooner. Or you can ask the lender to reduce the payment, so you pay less each month.
Most of my clients keep the payment the same. It is the option that saves the most total interest over the term of the mortgage.
Savings interest counts as income. Your personal savings allowance is £1,000 a year as a basic rate taxpayer, £500 as a higher rate taxpayer and nothing for additional rate taxpayers. Anything above that is taxed.
An offset saving is not income, so there is zero tax to pay on it. Tax on savings interest is also due to rise by 2 percentage points from April 2027, which makes offsetting more attractive for anyone with a larger savings balance.
Offset mortgage interest rates are often a little higher than the best standard mortgage deals. The question is whether your savings are big enough to make up the difference. As a rough guide, the offset deal wins when your savings are a significant share of the loan amount and you plan to keep them there.
If your savings rate after tax is higher than your mortgage rate, keeping the money in a savings account may be better. That is rare for higher and additional rate taxpayers.
If you have little in savings, or you expect to spend them soon on a new home or a car, the offset benefit will be small and you could pay a higher rate for nothing. A bigger deposit may do more for you, because it lowers your loan to value and can get you a cheaper fixed rate.
Our loan to value calculator shows how a larger deposit changes the rates you can get.
Fewer lenders offer offset mortgages than standard ones, but you can usually choose a fixed rate, a tracker or a variable offset product. When the initial deal ends, you move to the lender's standard variable rate unless you switch.
Check the product fee and any early repayment charge on the offset deal, as they can differ from the lender's standard range.
Offsetting works with either mortgage repayment method. On a repayment mortgage, the offset benefit speeds up your capital repayment. On an interest only mortgage, it lowers the interest payments each month, but the full mortgage debt is still due at the end.
With interest only, lenders will want to see a clear plan to repay, and your savings can be part of that plan.
Keeping your payment the same. A £200,000 repayment mortgage over 25 years at an illustrative 4.5% costs about £1,112 a month, with around £133,500 in total interest paid. Offset £30,000 of savings, keep the same payment and keep the savings in place, and the mortgage is cleared in about 21 years and 3 months. That is nearly four years sooner and roughly £50,400 less interest.
Reducing your payment instead. On the same mortgage, asking the lender to base your payment on £170,000 brings it down to about £945 a month, around £167 less. You pay less each month, but the total interest saving is smaller.
Offset vs savings for a higher rate taxpayer. £30,000 in a savings account paying 4% earns £1,200 a year. After the £500 allowance, 40% tax on the remaining £700 is £280, leaving £920. Offsetting the same £30,000 against a 4.5% mortgage saves around £1,350 of interest in the first year, with no tax to pay.
Is the higher rate worth it? Say a standard deal is 4.5% and the offset deal is 4.8% on a £200,000 loan. In year one, the standard mortgage charges about £9,000 of interest. With £20,000 offset, the offset mortgage charges about £8,640, so it wins. With only £10,000 offset it charges about £9,120, so it loses. On these figures, the break even point is about £12,500 of savings.
How does an offset mortgage calculator work? It takes your loan amount, interest rate, term and savings, then works out your interest as if the savings were taken off the balance. It shows how much interest you could save and how much sooner you could pay off your mortgage.
Do I earn interest in an offset account? No. Instead of earning interest, your savings reduce the interest you pay on the mortgage. For most people that is worth more, because the saving is at your mortgage rate and is not taxed.
Can I take money out of my offset savings? Yes, usually at any time. Your offset benefit falls while the money is out and goes back up when you put it back.
Are offset mortgage rates higher? Often slightly. That is why it is worth running your own figures, because the offset deal only wins if your savings balance is big enough to cover the difference.
Can family members offset their savings? Some lenders allow family offset, where parents or grandparents link their savings to your mortgage. The savings stay theirs, but they cannot use them freely while they are linked.
Can I overpay an offset mortgage? Yes, within the lender's limits. Overpaying lowers the debt permanently, while offsetting keeps your cash available. Our mortgage overpayment calculator shows how a lump sum compares.
