Contributions restricted by the donor must be used in accordance with any donor-imposed restrictions on that gift, whether the donor restricts a gift as to purpose or expenditure. Restricted gifts require additional tracking and accounting to ensure the funds are stewarded appropriately and used for the intended purpose. One type of restricted gift is an endowment.
Nonprofits with income-producing assets of $250,000 or more may need to register as a Charitable Trust with the Secretary of State.
Nonprofit Association of Washington’s Finance Unlocked for Nonprofits Toolkit goes deeper into nonprofit finance, including funds with donor restrictions. See Chapter 4, Giving.