The contact number XXX is already assigned to another contact. The contact number must be unique across all contacts.

Problem Statement

Xero returns "The contact number XXX is already assigned to another contact. The contact number must be unique across all contacts" when syncing from Chargebee because the contact number is already used by another Xero contact.

Solution

Map the Chargebee customer to the correct existing Xero contact so the integration uses that contact instead of creating a duplicate. Collect the following and send them to support:

A. The internal ID of the Xero contact to use: Open the contact in Xero and copy the ID from the URL (see screenshot).

B. The Chargebee customer ID that should be linked to this contact.

Chargebee will perform the mapping from the backend so the Chargebee customer syncs to the correct Xero contact.