# Code and Formats
source: https://developer.mastercard.com/eligibility-api/documentation/code-and-formats/index.md

* [Generic Code and Formats](https://developer.mastercard.com/eligibility-api/documentation/code-and-formats/generic-code-and-formats/index.md)
* [Eligibility Error Code](https://developer.mastercard.com/eligibility-api/documentation/code-and-formats/eligibility-error-codes/index.md)
* [Widget Error Code](https://developer.mastercard.com/eligibility-api/documentation/code-and-formats/widget-error-codes/index.md)

## Next Steps {#next-steps}

* Use the [Testing](https://developer.mastercard.com/eligibility-api/documentation/testing/index.md) guide to reproduce and validate the error scenarios documented here against Sandbox.
* Review the [API Reference](https://developer.mastercard.com/eligibility-api/documentation/api-reference/index.md) to confirm the request fields tied to each reason code.
* If an error persists after following the resolution steps, contact [Support](https://developer.mastercard.com/eligibility-api/documentation/support/index.md).