The term "4 net 7" on an invoice means that a 4% discount will be given on the price charged if payment is made within seven days of the invoice date. Essentially, the seller is offering a small discount as an incentive for the buyer to pay promptly. The "4" refers to the percentage discount, and the "net 7" means that the full amount is due in 7 days, after which the discount will no longer be available. This is a common payment term used in business transactions and can help both parties manage their cash flow.