Research basis for annual Greenhouse Gases emissions assessment is National and branch statistics data. Quality and confidence of Greenhouse Gases Inventory through assessment methodologies, preparation procedures and processing of data is confirm. Request at National Greenhouse Gases Inventory which contain assessment and analyses uncertainty elements on ІРСС-2000 and ІРСС-2006 are determine. Main approaches for uncertainty assessment in Environmental and Metrological Guides are considered. Applicates approaches GUM-1993 for Uncertainty Assessment in Greenhouse Gases Inventory are proposed.