The amendment to the Tax Code, which came into force on 1 January 2021, brings with it a number of changes. One of them is the adjustment of interest on arrears. Until the end of 2020, under Section 252 of the Tax Code interest on arrears corresponded to the annual amount of the REPO rate set by the Czech National Bank (ČNB) on the first day of the relevant calendar half-year, increased by 14 percentage points. From 2021, if the tax is not paid on time, such a misdemeanour is sanctioned by interest on arrears, which, compared to the 5th day after the tax is due in 2020, applies from the 4th calendar day. Furthermore, its daily amount is now governed by the Civil Code, whereas Section 252 of the Tax Code in point 4) stipulates that interest paid by a tax entity corresponds to the ČNB’s REPO rate as before, but newly increased by 8 percentage points. So, the amount of interest on arrears for the second half of 2020 was 14.25% p.a. and for the first half of 2021 8.25% p.a. In conclusion, it should be mentioned that according to the transitional provision of this amendment, the new interest rate will only apply to days of delay from 1 January 2021.