The upper limit of overdue fees stipulated by law is based on relevant Chinese laws and regulations, which can be explained in the following points:

1. Civil cases: For civil cases, the upper limit of overdue fees is The cap is usually calculated based on the interest rate on the amount payable. Under normal circumstances, the most commonly used is the benchmark interest rate stipulated by the People's Bank of China. According to the provisions of the "General Principles of the People's Republic of China and Civil Law" and other relevant laws and regulations, if the party fails to perform its obligations within the payment period agreed in the contract, it shall pay interest. The calculation method of interest, unless otherwise agreed in the contract, is based on the loan interest rate published by the financial institution.

2. Criminal cases: For criminal cases, the upper limit of overdue fines is generally not clearly defined. According to the provisions of the "Criminal Law of the People's Republic of China" and other relevant laws and regulations, when a party fails to pay fines, compensation, etc., if it is overdue, the court may determine the amount of overdue fines based on the specific circumstances.

3. Administrative penalties: For administrative penalties, the upper limit of late payment fees is usually determined by the administrative law enforcement agency. According to the "Administrative Penalty Law of the People's Republic of China" and other relevant laws and regulations, if a party fails to pay an administrative fine within the prescribed time limit, the administrative law enforcement agency has the right to require him to pay overdue fees. The amount of overdue fines is generally determined by the administrative law enforcement agencies in accordance with legal provisions based on specific circumstances.

In summary, the legal upper limit for late payment fees varies in different types of cases. For civil cases, the calculation is generally based on the benchmark interest rate; for criminal cases, in the case of overdue payment, the court has the power to determine the amount of overdue fines; and in administrative penalties, the amount of overdue fines is generally determined by the administrative law enforcement agencies.

Extended information: Late payment fees refer to the liquidated damages or late payment fees that need to be paid if the parties fail to perform their payment obligations according to the time limit stipulated in the contract or the law. The purpose of late payment surcharges is to encourage parties to fulfill their payment obligations on time and to make up for the economic losses caused to creditors due to late payment. In different types of cases, the provisions on late payment fees may vary and are defined by relevant laws and regulations. The amount of overdue fees can be assessed on a case-by-case basis, usually based on interest calculations, or determined by a court or administrative law enforcement agency.