While attempting to calculate tax, this error message is given:
"This is a duplicate of an existing Document' with unique index 'IX_Document_Unique and cannot be saved."
Microsoft Dynamics NAV
- This error message is caused when an invoice number in Dynamics NAV already exists as a DocCode in the Admin Console.
- Typically, the user is trying to release the document when this error occurs.
- To resolve this issue, the user will need to change the invoice number in Dynamics NAV to a number that does not exist in the Admin Console.
Note: This issue tends to occur when a live database has been restored to a test database. The user is then generating sample invoices in the test database and the AvaTax Configuration settings are still pointing to the Production company in the Admin Console.