When do late payment penalties apply and how are they calculated?

Late payment surcharges arise by operation of law solely as a result of the passage of time if a tax is not paid by the end of the due date. The late payment surcharge amounts to 1 % of the rounded down amount of tax in arrears for each month or part thereof; the amount is to be rounded down to the nearest amount divisible by fifty euros (§ 240 AO).