Abstract. The study analyzes the provisions of the Polish law concerning the principles of determining the digital description of building contour lines to be entered into the database of the real estate cadastre. The analyzed laws are contained in the Regulation on the register of land and buildings of 2001. The subsequent amendments to this Regulation regarding the contour of a building, made by the entry into force of the amending Regulations in 2013 and 2015, respectively, introduced significant changes. As a result of these changes in the definition of the contour of the building, some of the buildings, entered into the database of the real estate cadastre based on the previous wording of the provisions, became obsolete. The paper also analyzes the effects of the amendments to the Regulation on the register of land and buildings. Some of them should be considered positive, as the new provisions in the Regulation clarified to some extent the earlier wordings which were unclear and gave rise to ambiguous interpretation of the record data of buildings. However, some important record data of the buildings existing in the database of the real estate cadastre, such as the digital description of the contour lines and the resulting built-up area, became outdated as a result of another part of the amended provisions, although there were no changes in the structure of the buildings.
Key words: outline of the building, built-up area, cadastre, update of the database, building contour line