A spending policy is a set of rules and conditions that determine how a cryptocurrency wallet can be used to make transactions. It is a way of specifying the conditions under which a wallet can be used to spend funds, and it can be used to enforce certain constraints and requirements on the use of the wallet. Spending policies are commonly used in multisignature wallets, where they are used to specify the number of signatures that are required to spend funds, or to specify the types of transactions that are allowed. Spending policies are also used in other decentralized applications, such as in the management of funds for smart contracts, e.g. DAO treasuries, and in the creation of trustless escrow services.