SimpleTax

Stripe is a payments platform that handles card and alternative payment methods, subscriptions, invoicing, and the money movement around them. A developer integrates through an API and hosted or embedded components, and the platform absorbs the network of acquiring banks, card networks, and local payment methods behind that interface. The breadth is the reason it is the default choice for online businesses. Beyond accepting a payment, the platform covers subscription billing with proration and trials, usage-based metering, invoicing, tax calculation, fraud screening, and payouts to connected accounts. Each of those is a product in its own right that a team would otherwise build or buy separately. The tradeoff is cost and control. Pricing is per transaction and adds up at scale, which is why larger businesses negotiate rates or move some volume to a direct acquirer. The platform is also opinionated about the merchant of record and the payout model, so businesses with unusual money-flow requirements sometimes find the constraints binding.

Shopify is a hosted ecommerce platform. A merchant gets a storefront, a checkout, payment processing, inventory, and order management without operating any of it, and the platform handles the security and compliance work that accepting card payments requires. The product's scale comes from its app ecosystem. Anything the platform does not do natively — a loyalty programme, a subscription option, a review system, a warehouse integration — is available as an app, which means the platform can be extended without the merchant writing code. Themes control the storefront, and a headless mode exposes the commerce APIs for a custom frontend. The tradeoff is cost at scale and the constraint of a hosted model. Transaction fees apply when a third-party payment provider is used, app subscriptions add up, and the checkout cannot be fully customised outside the platform's extension points. Merchants with unusual requirements sometimes move to a headless platform to get that control back.