The Austrian legislator introduced the system of day fines in 1975 with the aim of reducing short-term imprisonment sentences and combating social inequality in sentencing. Since then, day fines are an important part of the Austrian sanctioning system. This chapter analyses the theoretical background of the Austrian model of day fines and compares it to other forms of monetary sanctions in fiscal and administrative penal law. In the judgment the court has to determine on the one hand the number of daily units depending on the severity of the offence and the guilt of the offender. The minimum number is two daily units, the maximum number of daily units depends on the offence committed and is provided for each offence separately (usually 360 or 720). On the other hand, the court has to determine the amount of the daily unit depending on the personal circumstances and the financial capacity of the offender (EUR 4 – EUR 5000). The amount of the fine is calculated by multiplying these two factors. For the case that a fine cannot be recovered, the court has to prescribe imprisonment in default of payment. Two daily units correspond to one day of imprisonment.