Overpaying the loan or saving the money instead

A mortgage overpayment is an extra payment on top of your standard monthly mortgage payment¹. It reduces the balance you owe, so you pay less interest, and if you keep up your normal monthly payment as well, it can shorten your term and bring the day you are mortgage-free forward¹.

Most mortgages let you overpay a certain amount, usually around 10% a year, without incurring any additional charges². That allowance is the single most important number to check before you pay anything extra, because going over it can trigger an early repayment charge³. The saving you make by overpaying is not taxed⁴, while interest on savings above your Personal Savings Allowance is taxed at your usual rate of Income Tax⁵.

So the choice is not simply "which rate is higher". It is a trade-off between a guaranteed, tax-free reduction in debt and keeping money accessible in a savings account that may be taxed. What follows sets out what overpaying does, what it costs, the limits that apply, and how the tax rules change the comparison.

What overpaying a mortgage means

An overpayment is simply paying a bit extra on top of your usual monthly payment⁷. On a repayment mortgage, where each monthly payment covers both the capital borrowed and the accrued interest⁸, that extra money goes straight against the capital you owe¹. Every time you overpay, you are paying off more of the capital, which reduces your mortgage balance¹. With a lower balance, the amount of interest you owe goes down too¹.

The effect is different on an interest-only mortgage, where your monthly payment covers interest but not the capital. Any overpayments you make still reduce the outstanding balance, which means the final payment you need to make to repay the loan is smaller and you pay less interest over the life of the mortgage¹. If you are on interest-only and want to overpay, you need to switch to a repayment mortgage to do this⁹.

Some lenders hold your overpayments in what is called an overpayment reserve. An overpayment reserve is what you create when you overpay your mortgage¹⁰. All overpayments go into the reserve, and the reserve is used to reduce the interest you pay on your mortgage balance¹¹. Depending on when you took out your current mortgage deal, that reserve could allow you to pay off your mortgage earlier, underpay on your mortgage, or borrow back the overpaid amount¹⁰.

Overpaying cuts the term and the total interest

Making overpayments means you will repay your mortgage quicker and pay less interest in total¹². As the balance reduces more quickly, your original mortgage term may shorten, enabling you to finish paying off your mortgage earlier¹³. Regular overpayments could help you become mortgage-free earlier if you maintain your normal monthly payment as well as your overpayment¹.

The size of the effect depends on how much you overpay and for how long. One worked example: an overpayment of £100 a month on a £200,000 mortgage could enable you to shave three years off the term and save as much as £10,000 in interest¹⁴. That is an illustration from 2021, and the actual saving on any mortgage depends on its rate and remaining term, but it shows the scale of what a modest regular overpayment can do over time.

There is a second, less certain benefit. Overpaying may mean that if you come to remortgage in the future, you might be able to choose from mortgages with lower interest rates because you would have a smaller loan-to-value ratio and more equity in your home, but it is not guaranteed¹. A lower loan-to-value ratio is simply the size of your loan measured against the value of your home¹⁵, and lenders price deals partly on that measure.

Limits, minimums and early repayment charges

Most mortgages have a limit or a maximum amount you can overpay before incurring an early repayment charge¹⁸. The typical allowance is around 10% of the balance each year², and most fixed-rate mortgages allow you to overpay up to 10% of the balance each year, either in regular overpayments or on an ad-hoc basis³. Overpaying more in a 12-month period may trigger an early repayment charge³.

The detail matters, because lenders define the allowance differently. Some run it by calendar year: one lender allows overpayments of up to 10% of your fixed rate loan amount each calendar year, January to December, without paying an early repayment charge¹⁹. Others express it as a percentage of the original loan amount rather than the current balance, and some products restrict overpayments to a maximum of 10% of your original loan amount before incurring an early repayment charge²⁰. Some lenders, but not all, let you overpay by up to 10% each year without a fee²¹.

An early repayment charge is a fee you may have to pay if your mortgage is repaid or transferred during the initial product period, or if you overpay more than the maximum allowed⁶. If you are still in your initial fixed or tracker period, you may be charged an early repayment charge for overpaying²³. Some mortgages have no limit at all on overpayments, though early repayment charges may still apply²⁴.

Check your lender's terms before you overpay

Make sure you check if your mortgage deal has overpayment limits or early repayment charges¹⁵. Customers should check their mortgage offer for any overpayment limits and early repayment charges²⁵. Always check with your lender as fees may be involved when overpaying²⁶. Depending on your mortgage product, there may be restrictions on the maximum amount you can overpay in one year without having to pay an early repayment charge²⁷.

The practical steps are straightforward. Find your mortgage offer or your lender's current terms, identify the annual overpayment allowance and how it is measured, and confirm whether an early repayment charge applies during your current deal period. If you are on a fixed rate, the allowance is usually stated as a percentage of the balance³. If you are on a tracker or another product, the position can differ: for some mortgage products there may be a limit to the amount you can overpay by and an early repayment charge could apply²⁸.

If you choose to make a lump sum payment, one lender's terms illustrate how the mechanics work: an early repayment charge may apply if the payment is made within the period that early repayment charges apply, and the borrower must confirm the payment is to repay the mortgage and should reduce the interest-charged balance²⁹. In other words, tell your lender what the money is for, so it is applied to the balance rather than sitting unallocated.

Will overpaying reduce my monthly payment or shorten my mortgage?

This is one of the most common points of confusion, and the answer depends on your lender and on what you tell it. Regular overpayments could help you become mortgage-free earlier if you maintain your normal monthly payment as well as your overpayment¹. That is the route that shortens the term.

Some lenders instead reduce your payment. For single overpayments of £500 or more, one lender automatically reduces your minimum monthly payments the following month, unless you have already changed your preference¹¹. If your aim is to shorten the term rather than lower the monthly bill, that is a preference worth setting with your lender in advance.

If you are struggling rather than overpaying, the options run the other way. Lenders may reduce your payments for a set period, charge interest only for a while on a repayment mortgage, give a payment holiday, or extend the mortgage term to reduce payments, depending on your payment history and whether your difficulties are long or short term³⁰. These options can reduce your monthly payments now, but they cost more over the lifetime of the mortgage³¹. A payment holiday does not write anything off: you still have to pay off the whole mortgage, either by increasing your monthly payments afterwards or by extending the mortgage term³².

Can I get overpaid money back if I need it later?

With some lenders, yes. An overpayment reserve is what you create when you overpay your mortgage¹⁰, and depending on when you took out your current mortgage deal, that reserve could allow you to pay off your mortgage earlier, underpay on your mortgage, or borrow back the overpaid amount¹⁰. That flexibility is the main argument for overpaying with a lender that offers a reserve, rather than treating the money as gone.

With other lenders, an overpayment is simply a permanent reduction of the balance, and the money is not available again. That is why the reserve question belongs in your checks before you pay, alongside the allowance and any charge.

There is a parallel in other areas of borrowing that shows how much difference the terms make. Overdrafts are repayable on demand, which means a bank can ask you to pay the whole amount back in one go if it chooses to³³. A mortgage overpayment held in a reserve is not repayable on demand in the same way, but the lesson is the same: the terms of the account decide what you can get back and when.

If you are considering overpaying but might need the money for something else, the reserve terms are the deciding factor. If your lender does not offer one, the money you overpay is committed to the mortgage.

Do I have to pay tax on savings interest when comparing the two?

This is where the comparison between overpaying and saving stops being a simple rate calculation. There is no tax on the saving you make by overpaying your mortgage⁴. The interest you earn on savings is treated differently.

Interest on savings is usually paid gross, which means tax is not automatically deducted before interest is paid³⁴. You pay tax on any interest over your allowance at your usual rate of Income Tax⁵. Any interest above your allowance is taxed at your standard income tax rate, whether that is 20%, 40% or 45%³⁵. If you do not already complete a Self Assessment tax return, you will need to register if your savings interest is more than £10,000⁵.

The rates are changing. From 2027, a basic-rate taxpayer will be faced with a 22% charge, higher-rate taxpayers will pay 42%, and those in the additional rate will pay 47%³⁶. Those figures are for a future tax year and are reported as planned changes, so they are worth checking against the position when the year arrives.

An offset mortgage changes the arithmetic again. With an offset mortgage, you will not pay any tax on savings income, or use up your Personal Savings Allowance, because you will not be earning interest on the cash³⁷. Instead, the savings are set against the mortgage balance so you pay interest on less. As an illustration, if you have £20,000 in a savings account that is linked to an offset mortgage of £300,000, you would only pay interest on £280,000³⁷. That structure suits higher-rate and additional-rate taxpayers in particular, because it removes the tax question altogether³⁷.

Is it better to overpay my mortgage or put the money in savings?

There is no universal answer, and the facts point in different directions depending on your circumstances. Overpaying gives a guaranteed reduction in the interest you owe, and the saving is not taxed⁴. Saving keeps the money available and earns interest, but interest above your Personal Savings Allowance is taxed at your usual rate⁵, and the rates are set to rise from 2027³⁶.

The factors that decide it are your mortgage rate, your savings rate, your tax band, and whether you might need the money. A higher-rate taxpayer with savings above the allowance faces a bigger tax drag on the savings route than a basic-rate taxpayer with savings inside the allowance. Someone who may need the money for repairs, a move or an emergency gets more from a savings account, or from a lender that offers an overpayment reserve¹⁰.

What overpaying cannot do is help if you have no cash buffer. Money paid into a mortgage is hard to get back unless your lender offers a reserve, and the terms of that reserve depend on when you took out your deal¹⁰. Keeping accessible savings alongside any overpayment is the arrangement that leaves both options open.

Where the protection stops

The rules that protect you when you overpay are mostly about disclosure and limits rather than compensation. Your lender must set out the overpayment allowance and any early repayment charge in your mortgage offer²⁵, and the charge itself is defined as a fee you may have to pay if your mortgage is repaid or transferred during the initial product period, or if you overpay more than the maximum allowed⁶. If you think a charge has been applied wrongly, or that the terms were not explained, you can complain to your lender and then to the Financial Ombudsman Service.

What protection does not do is make overpaying reversible. If your lender does not offer an overpayment reserve, the money is committed, and the only way to access it is to borrow again, which means a new application and a fresh affordability check. Lenders need to check whether you can afford to repay before you take out an agreement⁴⁰, and that applies to borrowing back money you have already paid as much as to any new loan.

The tax position is also outside any protection. Interest on savings is paid gross and you are responsible for paying the right tax on it³⁴, including registering for Self Assessment if your interest is more than £10,000⁵. Nobody will do that check for you.