LEGO does not have a formal buyback program for used LEGO bricks. However, there are several online marketplaces where you can sell your used LEGO bricks to collectors or other individuals who are interested in purchasing them. Some examples of these marketplaces include eBay, Etsy, and BrickLink. You could also try selling your LEGO bricks at a garage sale or through classified ads in your local newspaper or online. You can donate used LEGO bricks to the LEGO Replay Program described in this article.