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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.