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Every transaction in OMS moves through a predictable set of statuses. The top-level status is designed for programmatic branching. subStatus is always present and provides operational detail without complicating your core logic.

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Direction

Every transaction carries a sourceToDestination field: a composite of the source and destination instrument categories. OMS infers the direction from the source and destination instruments. You do not set it explicitly.

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Status model

The four top-level statuses are processing, awaitingAction, completed, and failed. A transaction begins at processing the moment it is created from a quote. awaitingAction is a non-terminal hold state; the hold object explains the reason and carries a deadline, and the transaction returns to processing once cleared. The hold object is discriminated by its type field: Each hold carries since, an optional deadline, and resolvedAt once cleared. Branch on status only. subStatus is always present. It is a status-scoped string carrying operational detail namespaced by its parent status (for example processing.fundsPulled, processing.cashPickupReady, or completed.cashPickupCollected). Each status carries a default member when no more specific value applies, so you always see a concrete sub-state on every transaction. Cash off-ramp lifecycle events surface here rather than as top-level statuses, and payout execution does too: processing.awaitingCryptoOut, processing.cryptoOut, processing.awaitingFiatOut, and processing.fiatOut track the crypto and fiat out-legs of a payout. Use subStatus for display and logging, not for control flow. The enum is open: new members may be added without an API version bump. If your client receives an unrecognized value, fall back to the status prefix before the dot (an unrecognized processing.someFutureThing still means processing).

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Failed transactions and returns

failed is terminal for the transaction, but not for the funds. When OMS has already received the inbound funds and the outbound leg cannot be completed, the funds are returned. Returns are executed by OMS operations, so no action is required from you, and are always made in the same asset that was received. The transaction’s subStatus tracks progress: Each step fires transaction.statusChanged, so you can render a “refund in progress” state without polling.

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Where returned funds go

The return path depends on how the transaction was created:

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Configuring return destinations

Deposit addresses and virtual accounts accept an optional returnDestination at create or PATCH. Send an explicit null in a PATCH body to clear one you set earlier. For a deposit address, returnDestination is a crypto target: a multi-asset OMS wallet (walletCrypto) or a registered external wallet (walletExternal), plus the network to return on, which must match the address’s expectedSourceNetwork. A custodial, non-multi-asset OMS wallet is rejected with 422 returnDestinationMustBeMultiAsset. For a virtual account, it is a fiat target: a registered bank account (bankUs, bankIban, or bankCanada), each with a required rail in network. USD bank rails are the only ones accepted today; the fiat balance wallet (walletFiat) and CAD (bankCanada with network: "local") are rejected with 422 railNotSupported.
Set a returnDestination on every deposit address and virtual account. Without one, returned crypto goes back to the on-chain sender, which may be an exchange hot wallet the customer cannot receive on, and returned fiat is held for manual processing.

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Webhook events

OMS fires a webhook on every meaningful state change. Each delivery carries the full transaction object under data, so your handler reads the status (and, if needed, subStatus) directly off it. Polling GET /transactions/{transactionId} is rarely necessary once webhooks are configured. Subscribe to events through the Webhooks endpoints or the OMS Dashboard. A subscription is an endpoint URL plus the list of event types you want:
Pass ["*"] in subscriptions to receive every event type, or list specific event names to filter. The Webhooks endpoints support full CRUD (GET/PATCH/DELETE /webhooks/{webhookId}) plus lifecycle actions (POST /webhooks/{webhookId}/enable | /disable | /rotate-key | /test), and the create response returns a signingKey once, which you use to verify the Webhook-Signature header on incoming deliveries. Inspect and replay delivery history at GET /webhooks/{webhookId}/deliveries and POST /webhooks/{webhookId}/deliveries/retry. Transactions emit one event, transaction.statusChanged, on every status transition described above, in either direction and on any rail. The full transaction arrives under data, so branch on data.status and use data.subStatus for detail. The envelope’s previousStatus names the status it left. To be notified when a transaction is held for compliance review, subscribe explicitly to transaction.fiatToCrypto.underReview, transaction.cryptoToFiat.underReview, or transaction.cryptoToCrypto.underReview; the * wildcard does not include them. See the webhook events catalog for every event type and the delivery envelope.

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Auto-created transactions

Deposit addresses, virtual accounts, and cash-ins bypass the quote step. OMS creates the transaction internally when funds arrive and moves it directly to processing. The same status model and webhook events apply.

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Idempotency

All POST endpoints accept an Idempotency-Key header. Use a stable key (UUID tied to your internal order ID) to safely retry on network failure. OMS returns the same response for any subsequent request with the same key within the idempotency window.
Set Idempotency-Key on every write request in production. It protects against double-execution without any coordination on your side.