I'm willing to bet there is not a way to print one check for all 300+ invoices for the vender. You'll probably just have to send two checks. Also note, that the check stub will not reference all of the invoice numbers, I don't remember the cut off amount, but I think it was around 15 invoice numbers that the check stub will reference. After that it says something like "and additional invoices". I would make a separate spreadsheet referencing all the invoices paid and attached with the check to avoid confusion.