An expendable endowment fund is a fund that must be invested to produce income. Depending on the conditions attached to the endowment, the trustees will have a legal power to convert all or part of it into an income fund which can then be spent. An expendable endowment differs from an income fund in that there is no actual requirement to spend the principal for the purposes of the charity unless or until the trustees decide to. However, income generated from expendable endowment is no different from income generated from permanent endowment, and should be spent for the purposes of the charity within a reasonable time of receipt (Charity Commission definition). See permanent endowment and spending out.