No screening system blocks all fraud without also blocking real customers. The controls below are tunable, and the right setting depends on your margin and your dispute rate rather than on a default.
How transactions are screened
Every transaction is scored before it is authorised. Most pass without the customer noticing anything; a small number are challenged, and fewer still are blocked.
- Risk scoring
- Device, location, velocity, card history and basket profile combine into a score. You choose the thresholds at which a payment is challenged or refused.
- 3-D Secure
- Shifts liability for fraudulent chargebacks to the issuer on authenticated transactions. Applied where the rules require it, and available on demand where they do not.
- Velocity rules
- Limits on attempts per card, per device and per address over a window. This is what stops card-testing runs.
- Allow and block lists
- Your own lists, by card token, email domain and address, which override the score in both directions.
- Manual review
- Borderline transactions can be queued for a person instead of being refused outright. Useful for high-value businesses where a wrong decline is expensive.
Card testing looks like a spike in declines
A sudden run of small failed payments usually means someone is testing stolen cards against your checkout. Tighten velocity rules first and tell us — you are not being charged for the attempts, but the pattern harms your acceptance rate.
What a chargeback is
A chargeback is the cardholder asking their own bank to reverse a payment. It is not a refund and it is not a request to you. The funds are removed from your settlement while it is investigated.
| Reason given | What it usually means | What wins the case |
|---|---|---|
| Fraud, card not present | The cardholder says they did not make the purchase. | Authentication data, or delivery signed for at the billing address. |
| Goods not received | Delivery is late, lost, or went somewhere unexpected. | Tracking that shows delivery, and your published delivery timescale. |
| Not as described | The customer is dissatisfied rather than defrauded. | The listing, the specification and your returns policy as shown at checkout. |
| Duplicate charge | Two authorisations, often after a retry. | Proof that the duplicate was already refunded, or that they are separate orders. |
| Subscription cancelled | The customer says they cancelled and were billed anyway. | Cancellation logs and the terms they accepted when subscribing. |
Refund first, argue later
If the customer has a point, refunding before the chargeback is raised costs you the sale. Fighting and losing costs you the sale, the fee and a mark against your dispute rate.
Defending a dispute
You are notified
The case appears in your dashboard with the reason code, the amount and the deadline. Deadlines are set by the scheme and cannot be extended.
Decide whether to contest
If the customer is right, accept it. Contesting a case you will lose costs more than accepting one you should.
Assemble evidence
Order record, delivery confirmation, communications with the customer, the terms shown at checkout, and any authentication data.
Submit once, properly
You get one submission. A clear, dated, one-page summary with attachments beats a pile of screenshots.
Await the outcome
The issuer decides. If you win, the funds and the chargeback fee are returned in full.
Preventing most of them
A large share of disputes are avoidable and have nothing to do with fraud. These five habits remove most of them.
- 1Use a billing descriptor customers will recognise. "Unknown merchant on my statement" is one of the commonest reasons a case is raised at all.
- 2Make your contact details easy to find. A customer who can reach you asks for a refund instead of calling their bank.
- 3Publish delivery timescales and send tracking. Most "goods not received" cases are impatience, not theft.
- 4Answer refund requests quickly. The cost of a fast refund is always lower than the cost of a dispute.
- 5Keep records for the full dispute window. Evidence you cannot produce is evidence you do not have.
Watch the rate, not the count
Schemes measure disputes as a percentage of transactions. A growing business can have more chargebacks and a healthier profile at the same time — the dashboard shows both.
Your obligations
- Keep your integration within PCI scope by never storing raw card data. Every route we offer is designed so you do not have to.
- Tell us before a major change in what you sell, your average ticket, or your delivery model.
- Do not process transactions for another business through your account. This is a serious breach and ends the relationship.
- Refund through the original transaction rather than by bank transfer, so the customer record stays intact.
Documents you may also need
Online Payments
Take payments on your own site: a hosted checkout, plugins for the major platforms, a direct API, and stored cards for repeat purchases.
Merchant ServicesSettlement & Payouts
When a payment becomes money in your account: settlement schedules, instant settlement, multi-currency payouts and how to reconcile them.
Merchant ServicesMerchant Pricing & Fees
What accepting payments costs: transaction rates, settlement options, hardware, chargebacks and the fees other providers leave until the contract.
This document was last updated on 1 August 2026. We publish the current version here at all times; superseded versions are available on request.
If anything on this page is unclear, write to us and we will explain it.