How do you correct a sent invoice?

[Partner]

I sent a "Paid" invoice to a client by mistake.  How do I reverse it?  I want to show that client still owes/has a unpaid balance.

[RHatch]

You can't change an invoice that is marked "Paid".  Once an invoice is marked "Paid" it becomes a transaction.  Only thing you can do now is return the transaction and start over.  Note: you can't take payments on an invoice.