Generally speaking, a looseleaf service is a consolidated source that contains the full text of primary sources such as statutes, regulations, and both judicial and administrative decisions, all related to a specialized area of law. Most services also contain commentary supplied by the editors to help clarify the primary source material, as well as to assist in locating additional materials on a topic. While often helpful, this commentary is not part of the primary source material so should not be considered authoritative.
Though they vary in format depending on the publisher, looseleafs have a number of features in common. The term "looseleaf service" is used to describe these publications because they usually appear in the form of binders that are frequently updated by the removal of old pages and the interfiling of new pages containing current material. Often a component of the looseleaf service is a weekly, biweekly, or monthly newsletter that calls attention to important new legislation, regulations, or cases. Older materials, particularly cases, may be removed from the binders and placed in soft or hard covered "Transfer Binders," or may be re-issued in hardbound reporter volumes.
Looseleaf services are widely used in practice, particularly in heavily regulated areas such as banking, securities, environment, and tax. They are often seen in their print format, though some publishers are making them available in web-based subscription versions. This format is popular with firms because it eliminates the need to file new pages each week. Some services are also available on Lexis and Westlaw.
Almost every looseleaf service contains a section entitled "How To Use This Service" or similar heading. Look for this section which often, but not always, appears in the first volume of the set. Spending a few minutes reading it can save you time and frustration later. These sections may also offer background information on the subject area such as administrative structure and important legislation.
Most services contain a section called "Finding Lists" or other similar name. This refers to lists, usually chronological, of documents by number, e.g. Rev. Rul. 72-575, with the paragraph numbers where the text of each document can be found within the service.
Services tend to have multiple "indexes," some of which are traditional subject indexes and some of which are really cross-reference tables that may list cases, statutes, or other materials. Every service has a subject index. If that is what you need, look for a "Topical Index" or "Index" near the beginning of the set. Usually the spine of the binder will show where the Index appears. Often, however, there will be more than one subject index - one "cumulative" and one or more others that update the cumulative one. Sometimes it is adjacent to the main index and sometimes the updating index is in a volume entitled "New Developments" or "Recent Developments" or similar title.
Note whether the references are to page numbers or paragraph (symbol ¶) numbers. A note at the top of the index page often tells you. Usually they are to paragraph numbers, which may be listed at the top or at the bottom of the page depending on the publisher. This system is used because of the looseleaf format. A paragraph number is assigned to a particular topic. Each paragraph number may cover as little as part of a page, or dozens of pages. Replacement or additional pages may be added as needed to that paragraph number without replacing the entire volume and its indexes.
You should always use any tables or "indexes" that provide "supplemental" or "recent" cross-references. These are usually organized by paragraph number; that is, look up the paragraph number where you found a primary source to see if more current material appears anywhere in the service. If in doubt, check with a librarian.
First, double-check to make sure your number is a paragraph number and not a page number. If it is a paragraph number, there are two possibilities. The first is that if the item you seek is a bit older, the pages containing it may have been moved out of the main binders in the set into the "Transfer Binders." Look at the date of the item you need and try to find a transfer binder for that period, then look for your paragraph therein. Transfer Binders are usually labeled as such and should be adjacent on the shelves to the main set; they are sometimes in soft covers, sometimes hardbound. Another possibility, particularly if the cite is quite recent, is that it appears in a special binder or section of a binder entitled "Current Developments," "Recent Reports," or something similar. Look for this section near the end or near the beginning of the set. If in doubt, consult the "How to Use This Service" section.