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

> Test your Instant Payments integration

# Sandbox Testing

Instant payments in sandbox use the same endpoints as production. Unlike ACH and wire transfers, instant payment statuses advance automatically in sandbox — you do not need to call a simulation endpoint to move an outgoing payment from `created` to `posted`.

A few practical notes when testing:

* **Routing numbers.** Lead does not publish a fixed list of designated sandbox routing numbers for instant payments. Any well-formed routing number can be used in the `creditor_agent.routing_number` (outgoing) or `debtor_agent.routing_number` (simulated incoming) field. The values shown in code examples (such as `987654321`) are illustrative, not reserved test values.
* **Availability checks.** Call `POST /instant_payments/check_availability` first to confirm the routing number is reachable on the network before sending.
* **Simulating an inbound payment.** Use `POST /v1/simulate/instant_payments/incoming` and supply your own `debtor_agent.routing_number`. The value is not validated against a real network.
* **Simulating a return.** Use `POST /v1/simulate/instant_payments/{instant_payment_id}/incoming_return` against an existing posted outgoing payment.

If you need a specific routing number to exercise a particular code path in sandbox, contact your Technical Account Manager.