BNPL instalments and the cost of a missed payment.
Each fortnightly instalment
—
Late fees
—
Effective cost if you miss
—
Your breakdown
Updates live as you type| Step | Amount |
|---|
How the fortnightly split works
Buy now, pay later services such as Afterpay, Laybuy, and Zip have become a default checkout button across New Zealand retail. The pitch is simple: take the goods today, split the price into equal instalments, usually four, paid every fortnight, and pay no interest. This tool does the basic arithmetic first, dividing your purchase into its instalments, then models the part the marketing skips over: what a missed payment actually costs. Because BNPL plans charge flat dollar late fees rather than interest, the tool multiplies the late fee by the number of payments you expect to miss and shows the effective total you end up paying.
It is worth being clear about what the calculator reports. It shows the instalment, the late fees, and the all-in cost if you slip, expressed as a percentage on top of the purchase. It does not convert that into an annual interest rate, because BNPL fees are not interest; they are fixed penalties. That distinction matters, and the next section explains why a small flat fee can still be a terrible deal.
A $500 purchase, four payments
Say you buy a $500 appliance and split it into four fortnightly payments. Each instalment is $125, and if you pay all four on time the appliance costs you exactly $500, with no interest. Now suppose cash is tight one fortnight and you miss a single payment that carries a $10 late fee.
A single $10 slip adds 2 percent to the cost of this purchase. That sounds minor, but read it through an annual lens. You were only ever borrowing $125 for roughly two weeks before the missed instalment. Paying $10 to defer $125 for a fortnight is, annualised, a borrowing cost in the hundreds of percent, well past what any credit card charges. The chart shows the four tidy instalment blocks and the small but disproportionate fee tacked on the end.
When interest-free turns expensive
BNPL is genuinely free if, and only if, every instalment clears on time. The danger is not any single purchase; it is stacking several plans at once so that multiple fortnightly debits hit the same pay cycle and one bounces. Late fees then compound across plans, and some providers pause your account or refer the debt onward. A practical rule I give people: before you tap the BNPL button, check that the fortnightly instalment fits inside your budget on your tightest pay fortnight, not your average one. If it only works on a good fortnight, you are one surprise away from a fee. BNPL providers in New Zealand operate under consumer credit rules that have been tightening, but the basic discipline sits with you, not the regulator.
Who BNPL actually serves well
Used with discipline, BNPL is a genuinely useful cash-flow tool, not a trap. Splitting a planned $500 purchase you can already afford across two pay cycles, simply to smooth the hit, costs nothing if you pay on time and can be smarter than draining your buffer in one go. The people it serves badly are those using it to buy things they cannot afford at all, where the fortnightly framing disguises a purchase that was never in budget. A quick self-test before you tap the button: would you still buy this if you had to pay the full amount in cash today? If the honest answer is no, splitting it into four payments has not changed the underlying problem.
Does buy now, pay later affect my credit score?
It increasingly can. Several providers now report activity to credit bureaus, and some run a credit check before approving larger plans. Missed payments and accounts in arrears can show up and dent your record, which matters if you are about to apply for a mortgage or car loan. Even where it is not formally reported, a lender reviewing your bank statements will see a row of BNPL debits and may treat them as committed spending that reduces how much they will lend you.
Is BNPL cheaper than a credit card?
Only if you always pay on time. A credit card paid off in full each month is also interest-free, and it builds a credit history while offering chargeback protection. BNPL beats a card you would otherwise carry a revolving balance on, but it loses badly the moment you miss a payment, because the flat fee on a small balance dwarfs a card’s interest. Match the tool to your own discipline: if you are confident every instalment clears, BNPL costs nothing; if you are not, a budgeted lump-sum purchase is safer.