Buy now, pay later - what Klarna and Clearpay actually cost
Buy now, pay later has become the default payment option at a large share of British online checkouts. Klarna, Clearpay, Zilch and PayPal’s instalment option all offer roughly the same thing: take the goods today, pay in instalments, and in the headline version pay no interest at all. That is genuinely a fair description of the product when it works. The problem is what happens at the edges, and how easily the edges arrive when several plans are running at once.
What you are actually signing up to
Most BNPL offers fall into one of two shapes. The short interest-free plan splits the purchase into three or four payments a fortnight or a month apart, with the first taken at the checkout. Used once, on something you could afford anyway, it costs nothing and is close to a free short-term loan.
The second shape is longer financing, spread over six, twelve or twenty-four months, and this one charges interest at a published annual rate. It is a consumer credit agreement with a friendlier interface, and the total cost is the number that matters rather than the monthly figure the checkout shows you. The buy now, pay later calculator will convert a monthly instalment back into what the purchase costs in total.
The gap between the two is significant, and the checkout does not always make it obvious which you are choosing. On a £600 purchase, the difference between three interest-free payments and a two-year financed plan is the difference between £600 and comfortably over £700.
The costs that do not appear at the checkout
Late fees are the obvious one. Interest-free plans generally charge a fixed fee when a payment fails, sometimes twice on the same instalment, and those fees are a meaningful proportion of a small purchase. A missed £25 payment that attracts two £6 charges has cost you almost half the instalment again.
The subtler cost is a weakened claim if the purchase goes wrong. Paying a retailer directly with a credit card brings Section 75 into play for anything over £100, as set out in our guide to Section 75 and chargeback. Interest-free BNPL sat outside those consumer credit provisions until 15 July 2026. A plan from a separate BNPL lender agreed since then gives you Section 75 rights against that lender, but an older plan does not, and neither does instalment credit the retailer provides itself. On those, the same £400 sofa can leave you with a weaker position when the retailer stops replying.
The third cost is behavioural and the hardest to price. Splitting a total into small instalments makes an expensive item feel affordable, which is precisely the effect it is designed to have. Research into instalment payments consistently finds that shoppers spend more when the option is available, which is why retailers pay to offer it.
What it does to your credit file
BNPL providers now share data with UK credit reference agencies, so plans can appear on your file and be visible to other lenders. What that means in practice depends on the lender: some treat a handful of well-managed instalment plans as neutral, while mortgage underwriters in particular tend to read multiple active plans as a sign of a stretched budget.
Missed payments are unambiguous. A default recorded against a BNPL agreement stays on your file for six years and affects mortgage applications, tenancy referencing and mobile contracts, all for a payment that may have been twenty pounds. The size of the debt has very little to do with the size of the consequence.
It is also worth knowing that interest-free BNPL from a separate lender has been regulated by the Financial Conduct Authority since 15 July 2026. Lenders now have to check that you can afford the plan and set out the repayments clearly before you agree, and complaints can go to the Financial Ombudsman Service. Instalment credit offered by the retailer itself stays outside those rules, so check who the lender is before assuming a particular protection applies to a plan you are being offered.
Buy now, pay later in numbers
- Instalments on a short interest-free plan
- 3 or 4
- Two £6 late fees on one missed £25 payment
- £12
- How long a default stays on your credit file
- 6 years
- Above this, a credit card brings in Section 75
- £100
When it makes sense and when it does not
Whether a plan is a sensible choice depends less on the provider than on the purchase and on what you already owe. The table sets out the common cases.
| Situation | Verdict |
|---|---|
| One interest-free plan, money already in the account | Fine, and effectively free |
| Spreading the cost of an unavoidable replacement, such as a broken washing machine | Reasonable, on the shortest term available |
| Longer financed plan at a published interest rate | Compare against a credit card before agreeing |
| Two or more plans already running | Stop, and clear the existing ones first |
| Buying something you could not pay for outright | The answer is no, whatever the terms |
| Clothing in sizes you are unsure about | Avoid; returns and instalments make a mess together |
| Any purchase over £100 where the retailer is unfamiliar | Credit card instead, the simplest route to Section 75 protection |
The pattern in that table is worth stating directly. BNPL is a reasonable tool for a single, deliberate purchase you could have paid for anyway, and a bad one for making an unaffordable purchase feel affordable. The question that separates the two is simple: would you buy this today if you had to pay the whole amount now?
If you already have several plans running
Start by listing them, because the most common failure mode is not knowing the total. Open each provider’s app, write down what is outstanding and what leaves your account in each of the next three months, and add it up. The combined monthly figure is almost always higher than people expect, because each individual plan was small enough to ignore.
Then clear the interest-bearing plans first and let the interest-free ones run to their end date, since paying those off early saves nothing. Turn off any setting that makes BNPL the default payment method, so that choosing it becomes a decision rather than a habit, and consider removing the stored card from the checkout of the shop you use most.
Summary
Three interest-free instalments on a purchase you could afford anyway cost nothing and are a perfectly sensible way to smooth a month. Longer financed plans are loans, missed payments are expensive out of all proportion to their size, and stacked plans are how people lose track of their outgoings. Run the numbers through the calculator before agreeing to anything with an interest rate attached, and if the purchase is over £100 and the shop is unfamiliar, use a credit card instead. Compare prices first on the deals page.