The act of managing a portfolio of a specific type of financial instrument/ product. For example, warehousing of swaps refers to holding a portfolio of swaps usually by a swap dealer without seeking to offset each swap with an identical mirror swap. In this sense, the swap dealer becomes a counterparty to every swap held in its portfolio. The dealer earns, for its services as a dealer, a pay-receive spread (bid-ask spread) which is equal to the difference between the swap coupon the dealer pays and swap coupon the dealer receives.

Warehousing is also referred to as running a book.