Forum Post: Importing outstanding customer invoices from old system

I am using a rapid start package to import all of the open invoices/Credit memos etc from my old system. I have created two sheet within excel, one for the sales header information and the other for the sales line information. I have managed to import all of the information and looks ok. When I try and batch post the invoices they all fail to post. If I post them individually they post fine. As you can imagine I with over 2 thousand entries I don't want to have to manually post them all. also when I imported I got the following message, please can someone advise on the cause of this and how to avoid this on my next import. Thanks for any help in advance. Regards