Integration: Transaction management and troubleshooting

Fixed-Rate transactions

To enable fixed-rate transactions, the following endpoints must be manually enabled upon your request: fixed-rate, v2/exchange, validate, markets, push, refunds, user_Id, and payloads. You will need to provide your project name, platform, and registration email for activation.

If a fixed-rate transaction is late or underpaid, the following rules apply:

— Late by 20+ minutes and unprofitable → canceled.

— Late but still profitable → processed.

— Underpaid but above the minimum → processed proportionally.

— Overpaid → halted and reviewed.

Deposit addresses and reuse

The payinAddress is not always the same; it changes. For memo-based coins like XRP and XLM, the address may repeat but the memo is unique.

However, users can reuse the same address. Even if it was sent months later, the system can process the deposit. You can use the continue or refund endpoints as needed. The specific endpoints to use are `/v2/exchange/refund` or `/v2/exchange/continue`.

Common Errors and Features

If you receive an error for `/v2/validate/address` for an asset like $SUI, it is because the endpoint supports a limited list of assets. For others, use regex, which is available upon request.

If a transaction is stopped and its status is "verifying", it has been flagged. Users are asked to verify via a SumSub link, which is valid for 3 days. After successful KYC, the exchange proceeds. Suspicious cases will be escalated.

Additional Information

— You can get coin images for your interface by using this endpoint: `https://api.changenow.io/v2/exchange/currencies?active=&flow=standard&buy=&sell=`

To enable the custody feature, go to the Custody tab in your business account, fill out the form, enable 2FA, and wait 2–3 days for approval. Once approved, deposit and withdrawal tools will be active.