We evaluated parliamentarians’ proposals between 1989 and 2020 to unravel the politicians’ interest in tax matters. During this period, 4,841 legislative proposals – bills, provisional measures or proposed amendments to the Constitution – dealing with tax matters were submitted to the Chamber of Deputies. However, according to the classification of a supervised algorithm (machine learning), only 5% of all legislative proposals on tax matters presented to the House in the period can be classified as progressive.