A promissory note is a legal document containing a promise to pay a sum to lender which includes the terms and conditions for payment, estimate of costs and the way in which interest rates and fees are calculated. The borrower is asked to sign the document to indicate their commitment and understanding as well as providing a promise to repay. Some loans require that you sign these documents each time you borrow whereas others, like the Federal Direct Loans, offer master promissory notes to make one or more loans for one or more academic years (up to 10 years).