Necessary and sufficient conditions to be fulfilled by a repayment schedule

Loan repayment is effected by series of installments paid by the borrower. These installments are the sum of principal and interest components charged to the borrower. However, not every schedule of principal and interest components that equals installment assures the recovery of the principal sum to the lender when the net present value of the installment at the rate charged to the borrower is worked out. Thus, necessary and sufficient conditions for the repayment schedule to be a standard schedule are provided in this research paper with needful justification.