> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fexco.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Rate source codes

> Optional source values and timestamps returned in DCC rate API responses.

Rate offer responses can include a source value. In Rate Service Connect,
`exchangeRate.source` can be absent or null. When present, it is a string;
do not assume a fixed set of source values.

## Rate sources

**Wholesale rate** describes the wholesale foreign exchange rate used for
DCC transactions. The source field identifies the provider or type of
rate, so the returned wording can differ between integration methods.

Preserve the value returned by the API; do not replace it with `Wholesale rate` when
parsing or storing the response.

In Rate Service Connect, the `exchangeRate.source` value can be
absent, null, or an unfamiliar string. Handle these values according to
your integration's requirements.

## Field names

The source field name depends on the integration method:

| Integration method | Field path |
| :- | :- |
| Rate Service Classic | `source` |
| Rate Service Connect | `exchangeRate.source` |

## Source timestamp

In Rate Service Connect, `exchangeRate.sourceTimestamp` can be
absent or null. When non-null, it is formatted as [ISO 8601](https://www.iso.org/iso-8601-date-and-time-format.html).
Do not assume every rate offer includes a source timestamp.

## Next steps

* [Request a DCC offer using Rate Service Connect](https://docs.fexco.com/dcc/guides/rate-service/dcc-offer-rate-service-connect.md):
  how to request a rate offer and interpret the `source` and
  `sourceTimestamp` fields in the response.
* [Request a DCC offer using Rate Service Classic](https://docs.fexco.com/dcc/guides/rate-service/dcc-offer-rate-service-classic.md):
  how to request a rate offer using the Rate Service Classic API.
* [Field mapping reference](https://docs.fexco.com/dcc/developer-resources/codes/field-mapping.md):
  how field names correspond across integration methods.


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