Apple kicked off a long-awaited iPhone trade-in program for its U.S. retail stores on Friday, the latest in its efforts to attract and retain customers for its smartphones.

The Cupertino, Calif. tech giant said its “reuse and recycling” program emphasizes the value of iPhones, even after they’ve been used.

“In addition to helping support the environment, customers will be able to receive a credit for their returned phone that they can use toward the purchase of a new iPhone,” a company spokeswoman said.

To get a credit, customers have to show that their trade-in iPhone works by powering it on. Customers also have to be in wireless carrier contracts when they leave the store, Apple employees said.

Trading in and buying a new phone through the program won’t re-start a customer’s contract, a person familiar with the process said. Additionally, if the cost of phone they’re buying is lower than the trade-in credit they receive, they’ll get a gift card with the remaining balance.

Apple isn’t the first company to offer compensation for used iPhones. A cottage industry has sprung up around recycling used gadgets, or reselling them on sites like eBay. Gazelle, which offers to buy used iPhones from customers through its website, indicates it will pay as much as $350 for a like-new device. Apple, in its stores, is offering as much as $280.