A promissory note, also referred to as a note payable in accounting, is a contract where one party (the maker or issuer) makes an unconditional promise in writing to pay a sum of money to the other (the payee), either at a fixed or determinable future time or on demand of the payee, under specific terms. They differ from IOUs in that they contain a specific promise to pay, rather than simply acknowledging that a debt exists.

The terms of a note typically include the principal amount, the interest rate if any, and the maturity date. Sometimes there will be provisions concerning the payee's rights in the event of a default, which may include foreclosure of the maker's assets. Demand promissory notes are notes that do not carry a specific maturity date, but are due on demand of the lender. Usually the lender will only give the borrower a few days notice before the payment is due.In the United States, the term lien generally refers to a wide range of encumbrances and would include other forms of mortgage or charge. In the U.S., a lien characteristically refers to non-possessory security interests (see generally: Security interest - categories).

In other common law countries, the term lien refers to a very specific type of security interest, being a passive right to retain (but not sell) property until the debt or other obligation is discharged. In contrast to the usage of the term in the U.S., in other countries it refers to a purely possessory form of security interest; indeed, when possession of the property is lost, the lien is released.[1] However, common law countries also recognize a slightly anomalous form of security interest called an "equitable lien" which arises in certain rare instances.

A mortgage is the pledging of a property to a lender as a security for a mortgage loan. While a mortgage in itself is not a debt, it is evidence of a debt. It is a transfer of an interest in land, from the owner to the mortgage lender, on the condition that this interest will be returned to the owner of the real estate when the terms of the mortgage have been satisfied or performed. In other words, the mortgage is a security for the loan that the lender makes to the borrower. The term comes from the Old French "dead pledge," apparently meaning that the pledge ends (dies) either when the
obligation is fulfilled or the property is taken through foreclosure.

In most jurisdictions mortgages are strongly associated with loans secured on real estate rather than other property (such as ships) and in some jurisdictions only land may be mortgaged. Arranging a mortgage is seen as the standard method by which individuals and businesses can purchase residential and commercial real estate without the need to pay the full value immediately. See mortgage loan for residential mortgage lending, and commercial mortgage for lending against commercial property.

A commercial mortgage is similar to a residential mortgage, except the collateral is a commercial building or other business real estate, not residential property. In addition; commercial mortgages are typically taken on by businesses instead of individual borrowers. The borrower may be a partnership, incorporated business, or limited company, so assessment of the creditworthiness of the business can be more complicated than is the case with residential mortgages.

Some commercial mortgages are no recourse, that is, that in the event of default in repayment, the creditor can only seize the collateral, but has no further claim against the borrower for any remaining deficiency. The general reason for this is twofold: many laws significantly prevent the creditor from going after the borrower for any deficiency, and mortgages structured for sale as bonds give a higher priority to constantly receiving some sort of income and therefore require a clause which allows the lender to take the property immediately, regardless of bankruptcy proceedings that the borrower might be going through.

The foreclosure process as applied to residential mortgage loans is a bank or other secured creditor selling or repossessing a parcel of real property (immovable property) after the owner has failed to comply with an agreement between the lender and borrower called a "mortgage" or "deed of trust". Commonly, the violation of the mortgage is a default in payment of a promissory note, secured by a lien on the property. When the process is complete, the lender can sell the property and keep the proceeds to pay off its mortgage and any legal costs, and it is typically said that "the lender has foreclosed its mortgage or lien". If the promissory note was made with a recourse clause then if the sale does not bring enough to pay the existing balance of principal and fees the mortgagee can file a claim for a deficiency judgement.