invoicing error message

[jrotty]

What does it mean to get the error message:"This ID has already been used. Please enter a different ID."

I am creating invoices and they are all different, to different customers and with different subjects, etc. It won't let me send the invoice when I get this message but it doesn't highlight what is incorrect

Help please

[EJ_]

It sounds like you might have accidentally entered in the same Invoice ID number, located in the "Details" section of the Invoice Template under the "Title" box.