The Federal Supreme Court’s decision of 18 May 2021 calls into question the recently enacted increase in the flat-rate deduction for property maintenance in the canton of Basel-Landschaft. As is customary in the cantons, property maintenance for privately used properties can be claimed either according to actual expenditure or as a lump sum. For buildings over 10 years old, the lump-sum deduction is 25%, and for buildings up to 10 years old, 20% of the imputed rental value. The complainants objected to the increase in the flat-rate deduction and claimed that extraneous motives had played a decisive role in the legislative process. According to them, the only reason for increasing the flat rate was to compensate property owners for the simultaneous increase in the imputed rental value. Although the Federal Supreme Court considered the flat-rate deduction of 20% of the imputed rental value for buildings up to 10 years old to be extremely high, it did not consider it to be untenably high. Thus, the appeal was dismissed and the provision was protected by the Federal Supreme Court.