When syncing a contact Xero returns the following error: The Account Number already exists
This error usually occurs when a contact with the account number has been archived.
When a contact with that account number has been archived, you will need to unarchive this contact, remove the account number from the contact record, then archive again.
When Xero contacts have been merged and the account number is saved on the archived merged contact, you can unarchive this contact, remove the account number, then merge and add this account number to the visible contact.
Please contact Xero support if you require further assistance.