The opportunities for Representatives to offer floor amendments to a bill or resolution depends on the procedures by which the House considers the measure.
The House's rules and precedents impose certain restrictions that apply generally to House floor amendments, regardless of the procedure under which they are offered.
In general, for example, an amendment is not in order (1) if the amendment is not in writing at the time it is offered; (2) if the amendment is in the third degree—that is, it is an amendment to an amendment to an amendment; (3) if the House already has acted on an identical amendment; (4) if the amendment only proposes to re-amend a portion of the bill that already has been amended; (5) if the amendment affects different parts of the bill and actually constitutes two or more amendments that can be offered en bloc only by unanimous consent; or (6) if the amendment is not offered at the time the Committee of the Whole is considering amendments only to the section or title of the bill that the amendment would affect. This list is not exhaustive, and there are exceptions to some of these general restrictions. For instance, an amendment to a substitute for an amendment is not considered to be a third degree amendment. Also, an amendment may re-amend something that already has been amended if it does so in the process of amending a larger part of the text in question.
In addition to such general restrictions, clause 7 of House Rule XVI also requires that each amendment must be germane to the text it would amend. This principle can be difficult to apply in practice.
Volumes 10 and 11 of Deschler-Brown Precedents of the House of Representatives devote almost 2,000 pages to the germaneness rule and its application. To be germane, it is not sufficient that the amendment be relevant to the bill the House is considering or even to the section or title of the bill that the amendment would change. It is possible for an amendment to be relevant without satisfying the technical standards of germaneness.
In the commentary that follows the text of the germaneness rule in the House Rules and Manual, the House parliamentarian identifies three tests of germaneness: subject matter, fundamental purpose, and committee jurisdiction. To be germane, (1) "[a]n amendment must relate to the subject matter under consideration," (2) "[t]he fundamental purpose of an amendment must be germane to the fundamental purpose of the bill," and (3) "[a]n amendment when considered as a whole should be within the jurisdiction of the committee reporting the bill."
None of these tests is always conclusive, nor is one of them necessarily more controlling than the others. Furthermore, an amendment may satisfy all three of these tests and still not be germane. To help explain this possibility, the parliamentarian also elaborates several principles of germaneness, including the following: (1) "[o]ne individual proposition may not be amended by another individual proposition even though the two belong to the same class," and (2) "[a] specific subject may not be amended by a provision general in nature, even when of the class of the specific subject," but (3) "[a] general subject may be amended by specific propositions of the same class."