Defense Primer: Budgeting for National and Defense Intelligence [Updated December 30, 2020] [open pdf - 493KB]
From the Introduction: "Intelligence Community (IC) programs include the resources (money and manpower) to accomplish IC goals and responsibilities as defined by the U.S. Code and Executive Order 12333. IC programs are funded through the: (1) National Intelligence Program (NIP), which covers the programs, projects, and activities of the IC oriented toward the strategic requirements of policymakers, and (2) Military Intelligence Program (MIP), which funds defense intelligence activities intended to support tactical military requirements and operations. The Director of National Intelligence (DNI) and the Under Secretary of Defense for Intelligence and Security (USD(I&S)) manage the NIP and MIP, respectively, under different authorities."
CRS In Focus, IF10524
Congressional Research Service: https://crsreports.congress.gov/