Forest Data Modernization Act of 2023 This bill modifies the Forest Inventory and Analysis (FIA) program of the Forest Service. Specifically, FIA must include forest carbon in its inventory. Further, FIA must carry out, as a data collection method, a timber products output study and a national woodland owner survey. FIA must include a clear definition of forest when reporting data. FIA's strategic plan must describe in detail the organization and procedures necessary to understand and report on changes in land cover and use, and evaluate carbon-related data variables. FIA must update the strategic plan not later than 180 days after this bill's enactment to include, among other things a plan to implement nationally consistent data collection protocols and procedures to improve the statistical precision of base program estimates; pathways to integrate and report on changes in forest carbon, including below-ground carbon; plans to collaborate with other federal agencies, nonfederal partners, and the private sector to integrate existing nationally available data sets and best available commercial technologies; and a plan to increase transparency and clarity in reporting. FIA (1) must establish an office, a data platform, or both to process and respond to complex data requests submitted by external organizations; and (2) may impose fees on the organizations submitting the requests.