How about this, rather than paying the price for those nice NCR forms, buy a copy of Quickbooks Pro. It will Print your invoices, statements, PO's, etc.
The only form you need to buy would be your checks & the program will do everything except sign those.
Few things are harder to put up with than the annoyance of a good example.
Microsoft Works (Which comes installed in most computers) and a little elbow grease and time will give you some professional looking invoices. I use the spreadsheets so the math is done for me and saves some time.
-Virgil Residential/Commercial Inspector 5 Star Inspections Member IAEI