The Senate votes on bills, resolutions, motions, amendments, nominations, and treaties in a variety of ways. If one-fifth of a quorum of senators request it, the Senate will take a roll-call vote. In a roll-call vote, each senator votes “yea” or “nay” as his or her name is called by the clerk, who records the votes on a tally sheet. In most cases a simple majority is required for a measure to pass. In the case of a tie, the vice president may cast the tie-breaking vote. In a few instances, the Constitution requires a two-thirds vote of the Senate, including: expelling a senator; overriding a presidential veto; proposing a constitutional amendment for ratification by the states; convicting an impeached official; and consenting to ratification of a treaty. Under Senate debate rules, it takes a three-fifths majority of those duly chosen and sworn to invoke cloture and end debate on a piece of legislation. Senate rules also require a two-thirds vote to invoke cloture on a measure that would amend the Senate's rules though the measure itself requires only a simple majority vote for adoption.
The Senate also conducts voice votes. In a voice vote the presiding officer states the question, then asks those in favor to say "yea" in unison and those against to say "nay." The presiding officer announces the results according to his or her best judgment. In a voice vote, the names of the senators and the tally of votes are not recorded.
The least common vote in the Senate is a division (or standing) vote. If a senator is in doubt about the outcome of a voice vote, he or she may request a division, whereby the presiding officer counts the senators voting yea and those voting no, to confirm the voice vote. Division votes are also commonly used for votes on treaties.
Finally, much of Senate business is conducted by unanimous consent, in which a measure passes so long as no senator objects.
The outcome of Senate votes are printed in the Congressional Record. The Senate's roll-call votes from the 101st Congress to present are available online.