Contact Push Limitation
The Xero API has a known limitation that does not allow 2 individual contacts with the same name to be pushed through to Xero.
Consider the following scenario:
In Xero there exists a contact with name 'John Doe', with the email firstname.lastname@example.org
When integrating with another system, we get another 'John Doe' contact, however with a different email address and contact details (email@example.com)
Because of this we will treat both John Doe records as separate contacts. However if we try to push the new John Doe into Xero, the Xero API rejects this on the basis that the name is a duplicate.
When this happens, we'll automatically append the second contact with a '-1' (John Doe-1) to send it through to Xero.