> ## Documentation Index
> Fetch the complete documentation index at: https://docs.paychainhq.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Core concepts

# Core Concepts And Terminology

Use these terms when reading the API, SDK, dashboard, and webhook docs.

| Term                     | Meaning                                                                                                 | Why it matters                                                             |
| ------------------------ | ------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------- |
| Business                 | A PayChain tenant that owns API keys, invoices, balances, webhooks, and billing.                        | Most API calls are scoped to one business.                                 |
| Customer                 | A reusable payer identity.                                                                              | Helps group invoices and recurring payment addresses.                      |
| Invoice                  | A payment request with amount, token, chain, network, deposit address, and status.                      | Invoice state is the source of truth for customer payment fulfillment.     |
| Deposit address          | The address a payer sends funds to.                                                                     | Some addresses are invoice-specific; some are reusable customer addresses. |
| Payment                  | A detected on-chain transfer related to an invoice or customer address.                                 | Only qualifying payments should affect revenue or fulfillment.             |
| Settlement               | The confirmed state after required chain confirmations and asset matching.                              | Use settled invoice state before releasing value.                          |
| Payout route             | An approved template for splitting an invoice after it is fully paid.                                   | Use for repeat split patterns.                                             |
| Dynamic payout recipient | One-time payout recipient supplied when creating an invoice.                                            | Useful for on-ramp, off-ramp, marketplace, or order-specific receivers.    |
| Withdrawal               | A treasury movement from PayChain-controlled business funds to a destination.                           | Programmatic withdrawals require payout API keys.                          |
| Webhook                  | A signed event delivered to a merchant backend.                                                         | Verify every webhook with the raw body before acting.                      |
| Balance                  | A treasury-facing view of available or reserved funds.                                                  | Use balances for operations; use invoice state for payment truth.          |
| Transaction              | A chain or platform movement used for reconciliation.                                                   | Helps explain what happened, but may not equal invoice truth by itself.    |
| Standard API key         | Backend API key for reads, customers, invoices, webhooks, balances, transactions, networks, and tokens. | It cannot move funds.                                                      |
| Payout API key           | Backend API key for constrained payout automation.                                                      | It can move funds only within policy.                                      |
| Sandbox                  | Test environment.                                                                                       | Do not mix sandbox credentials with live credentials.                      |
| Live mode                | Production environment.                                                                                 | Requires separate approval and production secret handling.                 |
| Chain / network / token  | Asset routing fields, such as EVM, Base, USDC.                                                          | Invoice and payout route assets must match exactly.                        |
| Gas credits              | USD-denominated allowance or prepaid balance used for sponsored outbound operations.                    | Gas exhaustion pauses eligible sponsored outbound actions, not receiving.  |
| Gas-blocked operation    | A sponsored outbound operation paused because gas credits are insufficient.                             | Top-up resumes queued operations oldest-first.                             |

<Warning>
  **Accounting note:** Invoice state and signed webhook events are the payment source of truth. Balances and transactions are reconciliation surfaces, not customer fulfillment proof by themselves.
</Warning>