Legal analysis: overdue dunning letters should be served within the limitation period. Some credit institutions require borrowers to sign a reminder letter in advance when borrowing money, which is easy to cause disputes. In fact, there is a three-year statute of limitations after the loan expires, which is enough time. Credit institutions need to protect their rights in time. It is not recommended for customers to sign dunning letters in advance, which is unnecessary.

Legal basis: Provisions of the Supreme People's Court on Several Issues Concerning the Application of Prescription System in the Trial of Civil Cases.

Article 3 If a party fails to raise the defense of limitation of action, the people's court shall not explain the issue of limitation of action, and shall take the initiative to apply the provisions of limitation of action to make a judgment.

Article 4 The people's court shall not support the defense of limitation of action put forward by the parties during the first instance, but the people's court shall not support it if it can be proved that the claim of the other party has expired according to new evidence.

The people's court shall not support the application for retrial or request for retrial on the grounds of the expiration of the limitation of action if the parties fail to raise the defense of the limitation of action in accordance with the provisions of the preceding paragraph.