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E-3-09, Acronyms and Glossary of Defined Terms: I (05/03/2023)


Independent Dispute Resolution

impasse process

An option available to an eligible lender to use to resolve loan-level disputes that were not resolved through the appeal process.

in-file credit report

An objective account, normally computer-generated, of credit and public record information obtained from a credit repository.

inclusionary zoning

A practice by which state or local governments impose zoning restrictions that require a specified percentage of new development in a designated area to be set aside to provide housing for low- and moderate-income persons.

income and resale price restrictions

Legally enforceable limits on maximum income for buyers and transferees of, and maximum permissible sales price for, a shared equity residential property; these are intended to keep the property affordable for subsequent purchasers.

income approach to value

A method of measuring the value of a property based on the market rent or income that the property can be expected to earn.

Independent Dispute Resolution (IDR)

IDR is a process that is available for eligible lenders to use to resolve loan-level disputes that were not resolved through the appeal, impasse, or management escalation processes.


A number used to compute the interest rate for an ARM. The index is generally a published number or percentage, such as the average interest rate or yield on U.S. Treasury bills. A margin is added to the index to determine the interest rate that will be charged on the ARM. This interest rate is subject to any caps on the maximum or minimum interest rate that may be charged on the mortgage, as stated in the note.

index disclosed to the borrower

The value of the selected index for an ARM that is given to the borrower when the mortgage is closed. When subsequent index values differ from this value, it reflects changes in market conditions.

initial interest rate

The original interest rate of the mortgage when it is closed. This rate (which is often referred to as the “start rate”) changes for adjustable-rate mortgages. Also referred to as the initial note rate.

installment debt

Borrowed money that is repaid in several successive payments, usually at regular intervals, for a specific amount and for a specified term (for example, an automobile loan or a furniture loan).

installment land contract

An agreement to transfer title to a property once conditions of the contract have been fulfilled. Also known as a contract or bond for deed.

institutional lender

A financial institution that invests in mortgages and keeps them in its own portfolio.

interest accrual rate

The percentage rate at which interest accrues on the mortgage. In most cases, it is also the rate used to calculate the monthly payments.

interest rate buydown plan

An arrangement wherein the property seller or any other party deposits money to an account so that it can be released each month to reduce the borrower’s payments during the early years of a mortgage. During the specified period, the borrower’s effective interest rate is “bought down” below the actual mortgage interest rate.

interest rate cap

For an adjustable-rate mortgage (ARM), a limitation on the amount the interest rate can change per adjustment or over the lifetime of the loan, as stated in the note.

interest rate change date

The date on which the mortgage interest rate changes for an ARM; the date on which interest begins to accrue at a new rate for an ARM MBS pool.

interest rate change interval

The period that elapses between interest rate change dates for an ARM.

interest rate differential

See yield difference.

interest rate shortfall

The interest rate shortage that occurs when Fannie Mae’s return on a mortgage (the net note rate) is less than Fannie Mae’s required yield.

interested party contributions

Costs that are normally the responsibility of the property purchaser that are paid (directly or indirectly) by someone else who has a financial interest in, or can influence the terms and the sale or transfer of, the subject property. These persons or entities include, but are not limited to, the property seller, the builder/developer, and the real estate agent or broker (or an affiliate who may benefit from the sale of the property and/or the sale of the property at the highest price possible).

intermediate-term mortgage

A mortgage that amortizes over an original term from 10 to 20 years.

investor-purchased mortgage insurance

Mortgage insurance coverage obtained by Fannie Mae after the purchase of a mortgage; a type of financial backing used for some second mortgages in lieu of borrower-purchased or lender-purchased mortgage insurance.


Internal Revenue Service

issue date

The first day of the month in which MBS backed by an MBS pool of mortgage loans are issued.

issue date principal balance

The principal balance of each mortgage in an MBS pool after crediting the principal portion of any monthly payments due on or before the issue date for the related MBS (whether or not it was actually collected) and after crediting any unscheduled partial payment or other recovery of principal received on or before the issue date (as long as it was not accompanied by payment of an interest amount that represented scheduled interest due for the month after the payment was made).