Overview
Two sensible instincts pull in opposite directions: clear what you owe before building anything, or never leave yourself without accessible cash. Get it wrong one way and you pay avoidable interest for years; get it wrong the other and you recycle the same debt every time something breaks.
This guide sets out a framework rather than a rule, in a fixed order: a small buffer first, then the arithmetic of comparing rates, then the exceptions that override it. The arithmetic is straightforward, but it has to be done after tax — and that is where most comparisons go wrong.
Quick Answer (Read This First)
Build a small emergency buffer first, even ahead of expensive debt. Without one, the next unexpected cost goes straight back onto the card and nothing is really being repaid.
After that, compare the interest rate on the debt against the after-tax return on savings. Where the debt rate is higher — for credit cards and overdrafts it currently is by a wide margin — overpaying wins, because interest avoided is worth more than interest earned.
Then check the exceptions: employer pension matching, genuine 0% promotional debt, priority debts, and facilities you could not reopen. If your debts are unmanageable rather than merely expensive, free advice comes before either decision.
Step One: A Small Buffer Before Anything Else
The strict arithmetic says clear expensive debt before saving at low single digits. Taken literally, that means holding no cash until the last card is cleared, and in practice that fails. With no accessible cash, every unplanned cost — a car repair, a boiler, an urgent journey — goes on credit, because nothing else can meet it. The balance you spent months reducing goes back up. The arithmetic was right about the rates and wrong about circumstances.
A modest buffer, commonly £500 to £1,000, absorbs most one-off shocks and breaks that cycle. It is not a full emergency fund: how much you need in an emergency fund covers the eventual target of three to six months of essential expenses. Keep the buffer instant-access and separate from your current account, so it is not absorbed into ordinary spending — where to keep an emergency fund sets out the trade-offs.
Step Two: The Arithmetic, Done After Tax
Once the buffer exists, compare the rate you are paying with the rate you are earning — but the two are not taxed the same way. Interest you earn can be taxable once it exceeds your Personal Savings Allowance: £1,000 for basic-rate taxpayers, £500 for higher-rate, nil for additional-rate. Interest you avoid by repaying debt is never taxed. A savings rate must therefore be reduced to its after-tax equivalent before comparison.
The gap in mid-2026 is not marginal. The Bank of England held Bank Rate at 3.75% on 30 July 2026, the fifth consecutive hold, and market-leading easy access accounts were advertising around 4.5% to 5.0% AER at the end of July. Borrowing sits in a different range entirely: Bank of England figures put the average credit card interest rate to UK households at around 24.7% in January 2026, and many major banks charge an EAR of about 39.9% on arranged overdrafts.
| Money at work | Typical rate, mid-2026 | Worth to you after tax |
|---|---|---|
| Arranged overdraft, many major banks | around 39.9% EAR | 39.9% avoided, never taxed |
| Credit card balance carried monthly | mid-20s to high-30s % | full rate avoided, never taxed |
| Market-leading easy access savings | around 4.5–5.0% AER | roughly 3.6–4.0% basic rate, 2.7–3.0% higher rate |
| Market-average easy access (Moneyfacts) | around 2.5% AER | roughly 2.0% basic rate, 1.5% higher rate |
| Cash ISA | varies by provider | not taxed, so headline equals net |
Those figures illustrate the market at the time of writing; rates move constantly and none is a quote. The point is the size of the gap. Clearing a balance costing 24% while holding taxable savings paying 4% loses roughly twenty percentage points a year, and no plausible rate movement closes that.
Compare like with like, too: savings are advertised as AER while borrowing is quoted as APR or EAR, as AER versus gross rate explains. Where interest falls within your allowance, the gross rate is the net rate — see how much interest is tax free and Cash ISA versus easy access. The order among several debts is separate: debt avalanche versus debt snowball covers the two standard approaches, and why overdrafts are often the most expensive debt explains why an overdraft often comes before a credit card.
IMPORTANT
Never overpay debt with money you will need back. Once a credit card balance is cleared, the cash is not yours to reclaim — you would have to borrow it again, on whatever terms are then available, and the facility may not still be there. This is why the buffer comes first.
The Exceptions That Override the Arithmetic
Four situations beat the rate comparison. They are genuine exceptions, not excuses to defer repayment.
Employer pension matching. A match is an immediate uplift on the money paid in — an effective return no consumer debt rate realistically matches, before tax relief. Contributing enough to capture the full match is usually the first call on income after the buffer, even ahead of expensive debt. The money is locked away until pension age, so it is a long-term commitment, not accessible saving; LISA versus pension covers how the wrappers differ.
Genuine 0% promotional debt. A balance at 0% costs nothing to carry, so there is no interest to avoid and saving wins. The condition is that it will actually be cleared before the promotional period ends, because the revert rate is typically high. That means a schedule, not an intention. What to check before a balance transfer and moving credit card debt to 0% cover the fees involved.
Priority debts. Some debts carry consequences far beyond interest: rent and mortgage arrears risk your home, council tax arrears can lead to enforcement, energy arrears to disconnection or a prepayment meter. These come before both saving and overpaying cheaper commercial debt, whatever rate is attached — see priority debts versus non-priority debts.
Facilities you could not reopen. Repaying to zero sometimes ends the arrangement. An overdraft can be withdrawn, an account closed for inactivity, and a facility obtained when your circumstances were different may not be available again. Where the borrowing is cheap and the access has real value, keep some liquidity alongside.
Mortgages Are a Separate Case
Mortgage debt does not belong in the same comparison as credit cards. The rate is normally far lower, the term is long, overpayment limits usually apply, and money overpaid is hard to retrieve unless the lender offers a borrow-back or the mortgage is an offset. The arithmetic is the same in principle — mortgage rate against after-tax savings return — but the constraints differ enough to be treated separately. Our guide on overpaying your mortgage versus saving works through the net-return comparison, including early repayment charges and overpayment allowances.
If the Debts Are Unmanageable, Neither Comes First
This framework assumes debts are expensive but under control: contractual payments are being met and the question is where surplus income goes.
If that is not the case — if minimum payments are being missed, if credit is being used for essentials, if balances rise despite payments — then the question is not saving versus overpaying but what solution fits your circumstances. StepChange, Citizens Advice and MoneyHelper all provide free, impartial debt advice. Asking early widens the options: how UK debt repayment plans work sets out the formal and informal routes, and there is no cost or credit-file consequence to simply asking.
Frequently Asked Questions
Looking for more on this topic? Browse all our savings guides.
Sources and Further Reading
This guide is based on UK regulator handbooks, official guidance and published market data. The following sources cover the rules and figures above:
- Bank of England — Bank Rate and monetary policy
- HM Revenue & Customs — tax on savings interest
- FCA Handbook — CONC (Consumer Credit sourcebook)
- Financial Services Compensation Scheme
Free, impartial debt advice is available from MoneyHelper, StepChange and Citizens Advice.
Related: Emergency Fund: How Much You Need | Debt Avalanche vs Debt Snowball | Overpaying Your Mortgage vs Saving | All savings guides.
