During Passover one is not allowed to own any Chometz (leavened products). As such there is a tradition that before the holiday we appoint the Rabbi to "sell" the Chometz on our behalf.
Our online 'Selling of the Chametz' has closed for 2018 . However you can still sell your Chametz at the main Chabad HQ website by clicking here
Full link here: https://www.chabad.org/holidays/passover/sell_chometz_cdo/jewish/Sell-Your-Chametz-Online