Principal debt is the money that the client receives directly from the lender to solve the tasks of the loan. It does not include interest, penalties in case of late repayment, other types of charges due to changes in the terms of the agreement. When the contract is signed, payment requirements are spelled out. Borrowers usually make monthly payments in equal installments. The fee includes the body of the loan, bank interest and other payments that are part of the principal amount owed to the bank.