noun
cross-selling
Business term for selling complementary products or services to existing customers.
銀行では、口座開設時に保険商品のクロスセリングを行うことが多い。
Banks often engage in cross-selling insurance products when customers open accounts.
アップセリング (upselling) encourages a higher-end version of the same product, while クロスセリング offers complementary items.
Borrowed from English 'cross-selling'.