In order to obtain the periodic amortization payments ( a_s ) of any loan with fractional interest payments you have to work with the effective rate of interest per time unit ( i^(m) ), because of that, if you do not enter this rate of interest, it is necessary to do the following conversion:

Once calculated the effective rate of interest per time unit ( i^(m) ), you have to know that in this kind of operation there is only one principal repayment( A_m ) per year, which is in the last amortization payments of each year ( a_m ), so the rest of the periodic amortization payments ( a₁...a_m-1 ) only pay interest ( I_s ). That is why the periodic amortization payments are calculated as follows:

• The last amortization payments of each year ( a_m ), if the loan has annual coupon that is the only amortization payments, is calculated with the following formula:
• The rest of the periodic amortization payments ( a₁...a_m-1 ) of each year is calculated with the following formula: