Adds a billing address to an existing checkout.
**Required Fields**
* email
* country_code
To prevent lost updates due to concurrent requests overriding changes made by others, it is recommended to enable optimistic concurrency control by including the `version` field in the request payload. If the provided version does not match the version on the server, a conflict error will be returned, which the client can handle accordingly.
Request
This endpoint expects an object.
country_codestringRequired
state_or_provincestringOptional
Represents state or province.
state_or_province_codestringOptional
postal_codestringOptional
phonestringOptionalformat: "^\+?[1-9]\d{1,14}(x\d{1-5})?$"
custom_fieldslist of objectsOptional
versionintegerOptional
The cart version that you expect to apply the updates. If the provided version doesn’t match the current cart version, you will receive a conflict error. This field is optional; if not provided, optimistic concurrency control will not apply.