Unfortunately you cannot void something that was posted originally as paid.  But you can just enter a negative invoice as paid for the same amount to reverse it.

The copy/paste feature is great, you just have to pay attention to the status, and the warning it gave you that it was going to post it as paid.  I have requested Sage add more to the warning to make it more obvious of the issue it causes but it hasn't happened yet.  It should say "warning: posting an invoice as paid will not affect your general ledger but it will affect your job reports and should only be used during implementation to bring in historical paid invoices:.

I have had issues with this myself in the past. Thank you for your answer. That is very helpful. I need to remember to hop in here and ask when I do have issues.  

Anytime.  Just remember to mark them as answered or completed please.

so I guess I have to use a clearing account