For a credit card that is overdue for three years, although the principal has been repaid, the overdue interest cannot be repaid. The following are detailed instructions:

1. According to regulations, overdue credit cards need to bear corresponding interest charges. Overdue interest is a fee incurred for failure to repay on time. It is a type of liquidated damages and is stipulated by banks to compensate for credit risks.

2. From a legal perspective, according to Article 147 of the Contract Law: “The parties shall perform their obligations in accordance with the agreement and shall not engage in other conduct that damages the purpose of the contract or hinders the other party from exercising its rights. "Even if the principal has been repaid, the overdue interest is still part of the contract and should be repaid as agreed.

3. From the perspective of lending relationships, credit cards are lending tools provided by banks to cardholders. Overdue payments violate the repayment obligations agreed by both parties. Even if the principal has been repaid, overdue interest is still one of the default liabilities that the borrower should bear.

To sum up, no matter from a legal perspective or from a lending relationship point of view, overdue interest cannot be repaid. Overdue interest is an account management fee set by the bank to compensate for credit risk. Therefore, even if the principal has been repaid, overdue interest still needs to be repaid in accordance with the contract or bank regulations.

Extended information:

Overdue credit card means that the cardholder fails to repay the debt on time after the specified repayment date, resulting in overdue fees and liquidated damages. Overdue interest is calculated based on the number of days overdue and the amount owed. Overdue interest is usually higher. Cardholders should make repayments strictly in accordance with the repayment date stipulated in the credit card contract to avoid additional fees arising from overdue payments.

It is worth noting that overdue credit cards will have a negative impact on personal credit records. In serious cases, they may even be included in the credit blacklist, which will affect personal future applications for loans, house purchases, credit cards and other financial services. Therefore, when using a credit card, it is very important to make timely repayments in order to maintain a good credit record and avoid the additional fees and inconvenience caused by overdue payments.