Cadastral systems belong to the most important public systems, since they provide necessary information for economic planning, spatial planning, and tax calculation, real estate denotation in perpetual books, public statistics, and real estate management as well as farm registration. They also provide source data to systems such as IACS and its main component LPIS. Quality of cadastral data has a major impact on the functioning many other systems. Legacy cadastral systems were developed using different data structures and various computer technologies. The quality of those legacy systems was sufficient for accomplishing everyday tasks but it was too low in the case of transferring data into other information systems. A practical approach to assure data quality in the process of transferring descriptive and geometric data from legacy systems into the Kataster OnLine - a modern integrated cadastral information system is presented in the paper.