Currently, there are two ways to calculate interest on credit cards in my country, one is penalty interest on the full amount, and the other is interest on the unpaid portion. Full penalty interest means that after the repayment date, regardless of whether the credit card has made partial repayments that month, as long as the full payment is not made, the card issuer will calculate interest on the cardholder based on the total consumption amount.

Credit card penalty interest calculation method 1: full penalty interest. If a cardholder spends 8,000 yuan on March 8, the bill received on April 7 will show that the "repayment amount for this period" is 8,000 yuan and the "minimum repayment amount" is 800 yuan. If the cardholder repays 800 yuan on the repayment date of April 25 according to the minimum repayment amount.

Then the recurring interest in the next statement on May 7 is: 8,000 yuan × 0.05% × 48 days (March 8-April 25) + 7,200 yuan × 0.05 % × 12 days (April 25-May 7) = 192 yuan + 43.2 yuan = 235.2 yuan. If you only repaid 7,999 yuan on the repayment date, which is 1 yuan less, then the recurring interest in the statement on May 7th is: 8,000 yuan × 0.05% × 48 days + 1 yuan × 0.05% × 12 Day=192.006 yuan.

Credit Card Penalty Interest Calculation Method 2: Interest on outstanding payments. The interest on the bill of 8,000 yuan underpaid is 0.03 yuan. The interest calculation on the unpaid part means that if the cardholder makes partial repayment, the repaid part can get interest-free treatment. Bank of China only calculates interest on the unpaid part. Interest is calculated based on the unpaid portion. The cardholder also consumed 8,000 yuan on March 8 and repaid 800 yuan according to the minimum repayment amount on April 25, the repayment date.

The 800 yuan returned by the cardholder on this day can enjoy the interest-free treatment from the consumption date to the repayment date. Then, on the bill on May 7, the recurring interest is: 7200 yuan × 0.05% ×60 days (March 8-May 7) = 216 yuan, which can save 19.2 yuan compared with the full penalty interest. If you repay 7,999 yuan on April 25, and you pay 1 yuan less, then the recurring interest in the statement on May 7 is: 1 yuan × 0.05% × 60 days = 0.03 yuan, and the interest will be less than the full penalty The interest rate is significantly reduced, and you can pay 191.976 yuan less.