If a book or other item needed by a library user is checked out or not available for some other reason, or if the library does not own the item, a registered borrower may have the privilege of filling out a form to request the item from another library. Some libraries permit interlibrary loan requests to be submitted electronically via e-mail or the World Wide Web.
Interlibrary loan (ILL) is a service that procures items or copies of items from other libraries for patrons. Some libraries assess ILL service charges to offset the costs of processing, postage, or the fees sometimes charged by lending libraries. Many ILL units refuse requests for current bestsellers, reference titles, special collections items, textbooks, or materials in a certain format (such as DVDs or electronic journals).
Regional library systems or campuses often have reciprocal lending agreements for ILL. Special postage for ILL items may also be available. How libraries use ILL, especially if they are a "net borrower" or a "net lender," can be a brief test of their collection strength.
Many interlibrary loan departments have procedures based loosely on copyright law. For example, if articles from a journal are requested a certain number of times within a certain time period, no more may be requested and the library must instead subscribe to that journal. Likewise, collection management decisions should be based on interlibrary loan statistics.
See also: interlibrary loan department