When creating a new post, the error message 'Payroll reference must be unique' will be displayed if the Post Reference field has been left blank or if the code entered here already exists as the post reference of another post.
To resolve this, when creating a post, make sure to enter a unique code in the Post Reference field which can be seen in the screenshot below.
Set up Auto Post Reference
If you would like to not have to add a post reference manually each time you create a post, you can also enable auto post reference, which will generate a new unique code automatically.
To do this:
Go to Setup and click Settings.
Click System Settings, then Global.
Search for Post Auto Reference and click it.
Tick the Boolean box.
Set the Boolean field to True.
Click Save.
