How online payments work: a plain guide for founders

Most founders know what a payment processor is in the way that most people know what a power grid is — they understand it exists and delivers something they need, but the mechanics are a mystery. That is fine until something breaks, fees spike unexpectedly, or a market expansion hits an unexpected wall. Understanding how online payments actually work will help you build better infrastructure, troubleshoot faster, and spend less.

The cast of characters

Every online payment involves at least five entities: the customer, your business (the merchant), the payment processor, one or more card networks, and the issuing bank that gave the customer their card. There is also often a payment gateway — software that captures card data from the customer and passes it to the processor — though many modern solutions bundle gateway and processor functions into one product.

The card networks — Visa, Mastercard, American Express, Discover — set the rules that govern the whole system. They determine what interchange fees are charged, what fraud standards apply, and how disputes are adjudicated. Processors are licensed to use these networks; they do not own them. Understanding this distinction helps clarify why interchange fees are largely non-negotiable regardless of which processor you use.

Authorization, clearing, and settlement

When a customer clicks pay, the flow goes like this: the payment gateway encrypts the card data and passes it to your processor. The processor sends an authorization request through the card network to the customer's issuing bank. The issuing bank checks the account balance, applies its fraud logic, and returns an approve or decline in a fraction of a second. If approved, the network sends an authorization code back through the chain to your checkout.

Authorization does not move money — it just reserves it. The actual transfer happens in two subsequent stages: clearing, where transaction details are reconciled across the network, and settlement, where funds are transferred from the issuing bank through the card network and processor into your merchant account. This typically takes one to three business days.

Why payments fail?

Payments fail for two broad categories of reasons: hard declines and soft declines. Hard declines mean the card is invalid, stolen, or the account is closed — there is no point retrying. Soft declines are temporary: insufficient funds, a fraud flag that can be cleared, a network timeout, or a processing error. Soft declines account for the majority of failed transactions, and most of them can be recovered with intelligent retry logic.

The practical implication for subscription businesses is that dunning management — the system for retrying failed subscription payments — can dramatically affect revenue. According to Stripe's billing data, smart retry logic that applies machine learning to find the optimal retry timing and method can recover more than a quarter of failed subscription charges that would otherwise churn.

For non-subscription businesses, having a fallback payment method request and clear checkout error messaging recovers a meaningful percentage of declined customers who would otherwise abandon.

Understanding what you are paying

The headline rate your processor advertises (say, 2.9% + $0.30) is typically the total fee, but what sits inside it matters. Interchange — the fee paid to the issuing bank — typically comprises the majority of that total. Card networks charge an assessment fee on top of that. Your processor adds their own markup. Premium rewards cards carry higher interchange rates than basic debit cards, which is why your effective rate varies by card type.

At higher volumes, moving to interchange-plus pricing — where you pay actual interchange plus a fixed processor markup — can reduce your effective rate meaningfully. Most processors offer this as an option once you are processing above roughly $50,000 per month.

Conclusion

Payments infrastructure is one of the least glamorous parts of running an online business and one of the highest-leverage. Every percentage point of authorization rate, every basis point of fees, and every hour of settlement time compounds across every transaction you process. The founders who treat payments as an active optimization surface rather than a set-and-forget vendor relationship consistently build more profitable businesses.