Prepaid cards in your first hundred: block only on data

Your free trial or paid checkout is live, and the first hundred signups are still small enough to read by hand. Block prepaid cards only when checkout data shows prepaid-funded trial abuse is material and you can afford the legitimate prepaid signups you will lose.

Prepaid cards are not automatically bad. Some real users use them for privacy, budgeting, or because they do not want a credit card on file. The problem appears when prepaid cards in trial signups are overrepresented in failed checkouts, inactive trials, or accounts that never convert. That pattern is what you are trying to catch.

At this stage, manual review beats clever automation. You can look at a handful of signups, ask a few users what card they used, and watch the next batch of checkouts. A growth tactic that needs scale is the wrong tool for your early cohort. You need a spreadsheet, a few conversations, and a reversible test.

The check is about material damage, not card labels

Material damage means lost revenue, wasted onboarding, or checkout clutter that makes real signups harder to see. A few prepaid trials are normal. A cluster of prepaid-funded trials that never activate is a signal. You want to separate the two before you block anything. The metric is trial-to-paid conversion, not just signup volume.

Stripe made funding_types_blocked available for Checkout Sessions and Payment Links in API version 2026-08-26.dahlia on August 26, 2026, alongside stripe-node 22.6.0 and stripe-python 15.6.0. Stripe's funding_types_blocked field accepts any combination of credit, debit, or prepaid and rejects a matching card while the customer is entering card details. Stripe's Checkout Session displays an error when a customer attempts to pay with a card whose funding type is restricted.

Stripe's funding_types_blocked restriction leaves prepaid cards already attached to active subscriptions unchanged, and it only controls new card entry through Checkout or a Payment Link. If you block prepaid cards, you are choosing to lose some legitimate signups in exchange for less trial clutter.

Stripe Radar, a fraud-detection system, uses a free-trial abuse model that weighs prepaid and virtual card indicators alongside card BIN, device fingerprint, and mismatch between IP and card country, and it flags such cards instead of automatically rejecting them based on that indicator alone. Visa limits subscription retry attempts to 15 reattempts per card in any 30-day window. The retry limit makes failed prepaid cards more than a nuisance when a subscription is trying to start.

The check comes before the block

Use the list below when you have enough signups to notice a pattern but not enough to run a full analytics stack. Each step exists to stop you from blocking on a hunch. The list moves from checkout friction through real usage and card-level evidence to a reversible test and the cost to legitimate users.

• Count checkout errors by funding type. Look for prepaid or virtual card errors clustered in a checkout path, an offer, or a signup source. If errors are scattered, keep watching.
• Compare trial activation to paid conversion. A prepaid-funded trial that never opens the product, never completes setup, or never returns is more suspicious than one that behaves like a real user.
• Look for prepaid and virtual card indicators. Check the flagged accounts for odd funding types, mismatched locations, or repeated attempts from the same device. A single odd signal is not enough.
• Test the block on new signups. Enable the restriction for new checkout attempts only, then watch whether errors drop and legitimate signups survive. Do not apply it to existing customers.
• Monitor lost legitimate prepaid signups. Ask a few blocked or bounced users what card they used and why. If real users are being stopped, the block is costing you more than it saves.

The block is a gate, not a cleanup

A prepaid block is a gate at the door. It does not clean up the accounts already inside. If you have prepaid-funded trials that are already active, review them by hand, ask questions, and decide what to do with them.

You are not trying to prove that prepaid cards are fraud. You are trying to prove that the damage is large enough to justify losing some real users. If the answer is no, leave checkout alone and keep doing the unscalable work: talking to users, watching behavior, and fixing the product.

If the answer is yes, keep the block narrow. Restrict new prepaid entry where the abuse is happening, review the flagged accounts, and stay close to the people who are being stopped. Adjust the block as soon as the signal changes.