> For the complete documentation index, see [llms.txt](https://docs.galaxypay.vn/upc/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.galaxypay.vn/upc/payment-gateway/appendix/response-codes.md).

# Response Codes

<table><thead><tr><th width="324">Response Code</th><th>Description</th></tr></thead><tbody><tr><td>200</td><td>Success</td></tr><tr><td>400</td><td>Bad Request (Due to missing required fields)</td></tr><tr><td>401</td><td>Unauthorized (Invalid API Key or Invalid Signature)</td></tr><tr><td>408</td><td>Transaction Expired</td></tr><tr><td>409</td><td>Transaction Duplicate</td></tr><tr><td>499</td><td>Transaction is cancelled by Customer</td></tr><tr><td>502</td><td>Bad Gateway (Cannot connect to Service Provider)</td></tr><tr><td>503</td><td>Service Unavailable (Cannot send request to Service Provider)</td></tr><tr><td>504</td><td>Request Timeout</td></tr><tr><td>505</td><td>Authentication Failure (3DS flow or Not Supporter)</td></tr></tbody></table>