Spreadsheet is not a bad idea. Some people do it with the help of VB and MS access. But after all I believe in professionalism in professional areas. We have lost one of our big client for invoicing issue. The client asked for double entry bookkeeping and while doing it two item was misspelled and one amount was duplicated. That happened only once in 4 years history with this client. But that gone absolutely wrong. And after that I always use bookkeeping software for making invoice template.