Billing is a product state machine
Connecting Stripe, a bank transfer or a crypto gateway does not create a billing system. A SaaS billing model must connect plans, entitlements, usage, invoices, payment state, settlement and access rules.
Plan → Entitlement → Usage → Invoice → Payment → Settlement → Reconciliation → Audit1. Separate commercial obligation from payment rail
The invoice or subscription obligation belongs to the SaaS domain. The rail may be cards, bank payments, USDC through CoinGate or a custom on-chain stablecoin flow. Changing the rail should not rewrite entitlement logic.
2. Model subscription lifecycle explicitly
Trial, active, past due, grace period, suspended and cancelled are business states. Upgrade, downgrade, proration and renewal need predictable rules and event handling.
3. Entitlements are not the same as a successful payment
A plan determines which capabilities and limits a customer receives. Entitlement decisions should be derived from the commercial model and product state, not scattered across checkout callbacks.
4. Managed USDC / CoinGate
For companies that want stablecoin checkout without building a crypto processor, a managed provider can become a payment rail. The SaaS keeps the order/invoice and entitlement model; the integration maps provider order state, callbacks, authoritative status checks, refunds and settlement into the internal ledger.
5. Custom on-chain rail
If on-chain payments are a native product capability, the architecture may include payment intents, dedicated addresses, chain observation, finality policy, an internal ledger, exception handling and treasury operations. The blockchain transaction still should not replace the SaaS billing record.
6. Reconciliation closes the loop
Finance needs to connect commercial obligations to provider orders, blockchain transactions, fees, settlement and bank or treasury outcomes. A durable reconciliation model makes differences visible instead of hiding them in manual spreadsheets.
7. Preserve auditability
Changes in plan, entitlement, invoice, payment state, refund and manual override should be traceable. Billing affects both access and money, so support and finance need a reliable history.