consignee_tax_id is now accepted under customs on POST /orders and POST /shipments, alongside the other customs declaration fields.
The old setup location still works and is marked deprecated in the spec, supported until at least September 2027.
If both are sent, the customs value is used. Responses echo the field in both places, so existing integrations are unaffected.
We recommend moving to customs.consignee_tax_id. See the API reference (developer.shipandco.com).
