BUSINESSES don’t let 13-year-olds pay for purchases with a promise. At least they didn’t before last week.

A new payment option for adults and teenagers without a credit card or a debit card has just become available. It’s initially offered by FooPets and Puzzle Pirates, online game companies that are business partners of Kwedit.com, a start-up based in Mountain View, Calif.

Minors as well as adults can buy items in the games with a “Kwedit Promise,” which can be paid off later in a number of ways  with a credit or debit card, for example, or with cash sent in a mailer that Kwedit supplies.

But here’s an entirely new payment option: A user 13 or older can print out a barcode and head to a 7-Eleven store, which will accept cash, scan the code and notify Kwedit that payment has been made. In the next three months, a Kwedit logo will join those for credit cards and other payment methods on the doors of all 7-Elevens, a company spokesman says.