trade-in
noun
COMMERCE /ˈtreɪdɪn/ ukus [ C or U ]
a way of buying a new car, machine, computer, etc. that involves giving your old one as part of the payment for it:
Second-hand car prices have fallen, resulting in lower trade-in values for buyers.
See also
part exchange noun
[ C ]
an old car, machine, computer, etc. that you give as part of the payment when you buy a new one:
All our stores take cars as trade-ins.