You can either pay the entire sum of the promissory note or pay it in installments.
When using an installment payment option, the borrower repays the lender in set payments over time—for example, 12 monthly payments for a year. There is also the option for a promissory note to be paid in installments with a final “balloon” payment made at the end of the agreed repayment schedule. So in a loan of $5000, the borrower could make monthly payments of $500 for six months and then make the final payment of $2000.
When repaying the entire sum of the note at once, you can either repay by a set due date or repay “on-demand” of the lender. If there is a “due on demand” payment option, the borrower will need to repay the lender when the lender requests that money.