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If your client's line of credit with differentiated form of payment, you are obliged to immediately calculate the monthly payment amount and specify it in the payment schedule.
The recalculation of the interest rate of the loan with differentiated form of payment must be made in the case, if the client makes a greater amount than specified in the payment schedule of loan repayment. For example, you granted a loan of 100 thousand rubles at 12% per annum for one year. The first month of repayment the interest rate will be calculated from 100 thousand roubles and will amount to 1200 rubles. Total payment for the first month of loan repayment will be equal to 8333+1200=9533 ruble. After making the first payment, the interest rate charged on the remaining loan amount and so monthly. As repayment of the loan the amount of interest will decline.
If your customer makes a monthly basis, not amount specified, and arbitrary, you must recalculate the remaining amount of debt interest. To do this, from the principal amount of the loan, deduct the total amount of payments made and the remaining numbers to calculate percentages.
Decorated in annuity payments the amount of the monthly loan repayment will be equal, regardless of what in fact paid the monthly payment. Calculate the monthly repayment amount using the loan calculator: http://www.helpkredit.com/zaemwiku/kalkulyatoru/annuitet.php. At the initial stage of repayment of the loan the interest will be much higher than the amount of the payment. As payment the amount of interest repayment is reduced, and the amount of principal repayment increases. But all this is reflected in the internal graph.
Make a recalculation in the event of an increase or decrease annual percentage rate. To increase or decrease the interest you can only from the time of contract renewal. For consumption consider only the remaining amount that is not paid by the client. To charge more or less interest on the entire outstanding loan amount you are eligible under any form of payments.