Debt Snowball vs Debt Avalanche: Which Repayment Method Works in the UK

If you have more than one debt and a bit of spare money each month, you have a decision to make: which one do you throw the spare money at? There are two well-known answers. The avalanche method says pay the highest interest rate first, because that is the debt costing you the most. The snowball method says pay the smallest balance first, because clearing something completely is the thing that keeps people going.

The avalanche wins on paper. The snowball wins more often in real life. That sounds like a fudge, so let us actually run the numbers and see how big the gap is.

The rules, briefly

Both methods start the same way. You pay the contractual minimum on every debt, every month, without fail. Missing a minimum triggers a late fee, possibly a default, and a mark on your credit file that sits there for six years. That part is not optional.

Then you take whatever you have spare and put all of it against one target debt.

• Avalanche: the target is the debt with the highest interest rate, regardless of size.
• Snowball: the target is the debt with the smallest balance, regardless of rate.

When the target is cleared, its minimum payment joins the spare money and the whole lot moves to the next target. That is why it is called a snowball: the amount you can attack with grows every time you finish one off.

A worked example with four debts

Here is a fairly ordinary set of UK debts. The rates are illustrative but they are the sort of spread most people are looking at: store cards at the top, a personal loan at the bottom, and an overdraft somewhere in between.

Total debt: £7,350. Total minimums: £225 a month. Say you can find another £150 on top, so £375 a month goes out in total.

Avalanche order: overdraft (39.9%), store card (29.9%), credit card (22.9%), loan (9.9%). You clear the whole lot in roughly 23 months and pay somewhere around £1,300 in interest.

Snowball order: store card (£450), overdraft (£900), credit card (£2,800), loan (£3,200). Same 23 months, and around £1,400 in interest.

The difference is about £100 across two years, or roughly £4 a month. That is the whole argument. Avalanche is mathematically better, and in this case it is better by less than a takeaway coffee a week.

Why the snowball keeps winning anyway

Debt repayment fails through abandonment, not through arithmetic. People stop. They have a bad month, the plan slips, and they quietly go back to paying minimums and pretending it is fine.

The snowball is built to prevent that. Clearing the £450 store card in month two gives you a finished thing. One fewer statement, one fewer login, one fewer direct debit. That is a real change you can see, and it arrives early enough to build the habit before enthusiasm wears off. The avalanche in this example gives you nothing to celebrate until month five.

If you are the sort of person who genuinely does not need that, use the avalanche and pocket the difference. Most people are not that person, and there is no prize for pretending.

The overdraft is usually the real problem

One thing the table above shows clearly: arranged overdrafts are frequently the most expensive money in the pile. Since the FCA's 2020 overdraft rules, banks must charge a single annual interest rate rather than daily or monthly fees, which made the true cost visible for the first time. A great many arranged overdrafts landed somewhere near 40% EAR, well above most credit cards.

Overdrafts also hide, because the balance never appears as a debt on a statement. It just looks like your current account is a bit emptier than it should be. If you are permanently £900 down and only ever briefly touch zero on payday, that is a £900 debt at 40%, and it should be near the front of the queue under either method.

Where both methods are the wrong answer

Neither method helps if the sums do not work. If your minimum payments plus essential costs already exceed your income, no ordering trick fixes that, and reshuffling the queue just delays getting proper help.

Signs you are past the point where snowball or avalanche is the right tool:

• You are using credit to cover essentials such as food, energy or rent.
• You are borrowing to make minimum payments on other borrowing.
• You have received a default notice or a letter before action.
• The total would take more than about seven years to clear at your current rate of payment.

At that point you want free debt advice, not a spreadsheet. StepChange, National Debtline and Citizens Advice are all free and none of them will try to sell you anything. Never pay a company to set up a debt management plan when the charities do it for nothing.

Worth knowing about too: Breathing Space, the government's debt respite scheme. A debt adviser can apply on your behalf, and it gives you up to 60 days during which creditors cannot take enforcement action, cannot contact you about the debts included, and cannot add interest or charges. There is a longer version for people receiving mental health crisis treatment, lasting for the length of the treatment plus another 30 days. You still have to keep making your ongoing payments where you can, and you cannot use the standard version twice in 12 months.

Things that beat both methods

Before you agonise over the order, check whether you can cut the interest rate instead. Two options are worth an hour of your time.

A 0% balance transfer card. If your credit file is decent, moving expensive card debt to a 0% deal converts interest into a one-off transfer fee, typically a few per cent of the balance. The rule is simple: work out the monthly payment that clears it inside the 0% window, set that as a standing order, and never spend on the card. If you cannot clear it in the window, you need to know what the rate reverts to before you apply.

A credit union loan. Credit unions in Great Britain are capped by law at 3% a month on the reducing balance, which works out at 42.6% APR at the very top, and most lend well below that. The cap in Northern Ireland is lower again. That is not cheap in absolute terms, but for someone consolidating a 39.9% overdraft and a 29.9% store card it can still be an improvement, and credit unions will often lend where a bank will not.

What almost never helps is consolidating into a longer loan at a similar rate. The monthly payment drops, which feels like progress, and the total interest goes up because you are borrowing for longer. Check the total amount repayable, not the monthly figure.

Setting it up so it runs itself

Pick your order, then automate it. Standing orders for every minimum, dated for the day after payday so the money leaves before you can spend it. One more standing order for the extra amount, going to the target debt. Review it the day a debt clears, and only then, because checking daily is how people talk themselves out of plans.

Write the order down somewhere you will see it. A list of four debts with the target circled is a better motivational tool than any app, mostly because you cannot swipe it away.

If you want to see what is genuinely spare each month before you commit to a figure, run your spending through the expense tracker first. Committing to £150 a month when the real number is £80 sets the plan up to fail in month three.