The day-fine system was first introduced in Finland in 1921 and then in Scandinavian countries such as Sweden in 1931 and Denmark in 1939, in Germany and Austria in 1975 and in France in 1988, and it has also been adopted in many other countries including Hungary, Norway, Poland, Switzerland and Portugal. Under a day-fine system, stating the number of fine days shows the offender's culpability outwardly, satisfying the culpability principle, and because the daily amount differs by grade according to the offender's financial situation, it can also satisfy the principle of equal sacrifice.

So, at least in theory, the day-fine system removes the drawbacks of the fixed-sum fine system, which either ignores the offender's financial situation or takes it into account only by guesswork at the judge's discretion, and achieves justice in fines by individualizing the penalty. Fines have a special character that sets them apart from other penalties. For other penalties, the length of punishment is proportionate to wrongdoing and culpability, so the 'principle of equal sacrifice,' the standard of fairness in punishment, and the 'culpability principle,' its basis of legitimacy, are automatically satisfied.

Even when life is forcibly taken or qualifications and liberty are forcibly taken away, the same length is regarded as the same suffering. With fines, however, even if people pay the same fine for acts of the same wrongdoing and culpability, their financial situations differ, so in reality people with less financial ability or property suffer more, departing from the principle of equal sacrifice. On the other hand, if fines for the same crime are graded according to financial circumstances, the amount of the fine no longer tracks the degree of wrongdoing or culpability, departing from the culpability principle.

If a fine reflects the offender's financial circumstances but is too large, it can strip away the person's economic foundation or turn into a substitute custodial sentence, losing the advantages of a fine, and if it is too small, it loses its punitive effect. The difficulty in running a fine system is how to reflect differences in offenders' financial situations, and the day-fine system was devised as a solution to this problem. The day-fine system reflects a shift in criminal justice ideology that places more weight on 'sentencing based on justice' than on 'the offender's return to society through correction.'

Running a day-fine system would make it easier for offenders to accept both a fine amount that meets the demand for equal sacrifice and the authority of the criminal justice system, because fines would be imposed according to each offender's financial condition. If courts used their broader discretion over fine amounts to widen the use of fines, custodial sentences would become a last resort. Compared with the fixed-sum fine system, which reflects the seriousness of the crime and the offender's finances without order or system, judgments would become more rational and precise, and the system would also cope more easily with inflation.

The term noblesse oblige is a French phrase meaning the moral responsibility and duty required of people of high status and rank.

To add: Article 70(2) of the Criminal Act, added in May 2014 after the emperor labor controversy, requires courts to set a detention period of at least 300 days for fines of 100 million won or more but under 500 million won, at least 500 days for fines of 500 million won or more but under 5 billion won, and at least 1,000 days for fines of 5 billion won or more. The cap on workhouse detention is still three years (Article 69(2)). As of 2026 Korea has not adopted day fines, and under the Special Act on the Execution of Community Service for Fine Defaulters, in force since 2009, people who cannot pay a fine can apply for community service instead of detention. France adopted day fines in 1983.