1/15 net 30 date of invoice translates as. a 1 percent discount may be taken on 15 percent of the purchase if the account is paid within 30 days after the end of the month a 1 percent cash discount may be taken if paid in 15 days; if no cash discount is taken, the balance is due 30 days after the invoice date a 1 percent cash discount may be taken if paid in 15 days; if no cash discount is taken, the balance is due in 30 days after the middle of the month a 1 percent cash discount may be taken if paid in 15 days; if no cash discount is taken, the balance is due 30 days after the end of the month