The refundable charge, which is already levied on Oyster pay as you go cards, will be paid when passengers who buy or replace replace a misplaced, unregistered card.
According to TfL, season ticket holders account for the majority of the wasted cards. Official figures suggest a third of all new Oyster cards issued with a 7 Day Travelcard or Bus & Tram Pass on them are discarded after a week and more than half within 5 weeks.
Shashi Verma, TfL Director of Fares and Ticketing said: “To encourage Londoners to keep hold of their cards a £3 refundable deposit will be payable for all new Oyster cards issued from the 17th May. We are aiming to cut the million cards wasted every year which will save £3m in administration costs which we will plough straight back in to improving the transport system.”