I had an invoice with 14 entries on it that I had to void and a year later recreate. I thought it would be easiest to make a copy in QB of the original invoice and then just go down and re-enter the hours (I copied off the original invoice that I found in my email). The problem now is that the estimate shows those hours as unbilled and that is not great - I don't think my method was a good one, I would caution anyone who bills off estimates not to do this.