The NIH Congressional Justification ("CJ") provides the Senate and House Appropriations Committees detailed estimates and justifications for research and research support activities (infrastructure, administrative, etc.) that NIH would anticipate funding at the President's Budget Request level.
The Overview 
section provides a narrative discussing NIH's past accomplishments in advancing the biomedical research enterprise, as well as current and future research endeavors of great promise. This section also provides NIH budget and employment summary tables (consolidated from those of all NIH's Institutes and Centers) and, justifications and tables for centrally provided services (the NIH Management Fund, and the NIH Service and Supply Fund).
NIH has 27 separate appropriations for which CJ documentation is prepared. Links to this documentation is provided here: Institutes and Centers Congressional Justifications
Please note that the Overview section and the justification for the National Institute of Allergy and Infectious Diseases (NIAID) do not reflect the amendment to the FY 2021 PB request for NIAID released by the Office of Management and Budget on March 17, 2020.