What determines whether the US House votes by voice, roll call, or unanimous consent?
[Note that in the following a "recorded vote" vote is a roll call vote. The House only uses a roll call vote when the electronic system is unavailable.]
Congressional Research Service, The Legislative Process on the House Floor: An Introduction, Updated May 20, 2019.
Legislation is sometimes brought before the House of Representatives for consideration by the unanimous consent of its Members. Long-standing policies announced by the Speaker regulate unanimous consent requests for this purpose. Among other things, the Speaker will recognize a Member to propound a unanimous consent request to call up an unreported bill or resolution only if that request has been cleared in advance with both party floor leaders and with the bipartisan leadership of the committee of jurisdiction.
Voting and Quorum Procedures
Whenever Representatives vote on the floor, there is almost always first a “voice vote,” in which the Members in favor of the bill, amendment, or motion vote “Aye” in unison, followed by those voting “No.” Before the Speaker (or the chair of the Committee of the Whole) announces the result, any Representative can demand a “division vote,” in which the Members in favor stand up to be counted, again followed by those opposed. But before the result of either a voice vote or a division vote is announced, a Member may try to require another vote in which everyone’s position is recorded publicly.
This recorded vote is taken by using the House’s electronic voting system. In Committee of the Whole, an electronic vote is ordered when 25 Members request it. In the House, such a vote occurs when demanded by at least one-fifth of the Members present. Alternatively, any Member can demand an electronically recorded vote in the House if a quorum of the membership is not present on the floor when the voice or division vote takes place.
The Constitution requires that a quorum must be present on the floor when the House is conducting business. In the House, a quorum is a majority of the Representatives; in Committee of the Whole, it is only 100 Members. However, the House has traditionally assumed that a quorum is always present unless a Member makes a point of order that it is not. The rules restrict when Members can make such points of order, and they occur most often when the House or the Committee of the Whole is voting. In the House, for example, a Representative can object to a voice or division vote on the grounds that a quorum is not present and make that point of order. If a quorum is not present, the Speaker automatically orders an electronically recorded vote during which Members record their presence on the floor by casting their votes. The issue is decided and a quorum is established at the same time. A voice or division vote is valid even if less than a quorum participates in the vote so long as no one makes a point of order that a quorum is not present. For this reason, Members can continue to meet in their committees or fulfill their other responsibilities off the floor when the House is doing business that does not involve publicly recorded votes.