Forest net biome exchange and carbon stock projections with uncertainty by regions of the mainland Finland over period 2015-2050. Projections under three climate scenarios, RCP2.6, RCP4.5, and RCP8.5, and four harvest scenarios - BaseHarv (historical average harvest level of the years 2015-2021), slightly more intensive harvests MaxHarv (1.2 x BaseHarv), lower harvest intensity LowHarv (0.6 x BaseHarv) and no harvests after the year 2021 NoHarv - for each administrative region (NUTS3), and as aggregated from all the regions to the whole country, are given. The files contain mean value and 2.5%, 5%, 25%, 75%, 95% and 97.5% quantiles of the average Net Biome emissions (file NBEave.xlsx) and total carbon stock (file Cstockave.xlsx). The forest areas (forest land and poorly productive forest land, excluding undrained peatlands), and areas of mineral soils and drained organic soils for each region and the whole mainland of Finland are given in file areas.xlsx. Description of the used data and methods are given in article: Junttila, V., Minunno, F., Peltoniemi, M. et al. Quantification of forest carbon flux and stock uncertainties under climate change and their use in regionally explicit decision making: Case study in Finland. Ambio (2023). https://doi.org/10.1007/s13280-023-01906-4