Senate Rule XII - Voting procedure

111th Congress
1. When the yeas and nays are ordered, the names of Senators shall be called alphabetically; and each Senator shall, without debate, declare his assent or dissent to the question, unless excused by the Senate; and no Senator shall be permitted to vote after the decision shall have been announced by the Presiding Officer, but may for sufficient reasons, with unanimous consent, change or withdraw his vote. No motion to suspend this rule shall be in order, nor shall the Presiding Officer entertain any request to suspend it by unanimous consent.

2. When a Senator declines to vote on call of his name, he shall be required to assign his reasons therefor, and having assigned them, the Presiding Officer shall submit the question to the Senate: "Shall the Senator for the reasons assigned by him, be excused from voting?" which shall be decided without debate; and these proceedings shall be had after the rollcall and before the result is announced; and any further proceedings in reference thereto shall be after such announcement.

3. A Member, notwithstanding any other provisions of this rule, may decline to vote, in committee or on the floor, on any matter when he believes that his voting on such a matter would be a conflict of interest.

4. No request by a Senator for unanimous consent for the taking of a final vote on a specified date upon the passage of a bill or joint resolution shall be submitted to the Senate for agreement thereto until after a quorum call ordered for the purpose by the Presiding Officer, it shall be disclosed that a quorum of the Senate is present; and when a unanimous consent is thus given the same shall operate as the order of the Senate, but any unanimous consent may be revoked by another unanimous consent granted in the manner prescribed above upon one day's notice.

109th Congress
1. When the yeas and nays are ordered, the names of Senators shall be called alphabetically; and each Senator shall, without debate, declare his assent or dissent to the question, unless excused by the Senate; and no Senator shall be permitted to vote after the decision shall have been announced by the Presiding Officer, but may for sufficient reasons, with unanimous consent, change or withdraw his vote. No motion to suspend this rule shall be in order, nor shall the Presiding Officer entertain any request to suspend it by unanimous consent.

2. When a Senator declines to vote on call of his name, he shall be required to assign his reasons therefor, and having assigned them, the Presiding Officer shall submit the question to the Senate: "Shall the Senator for the reasons assigned by him, be excused from voting?" which shall be decided without debate; and these proceedings shall be had after the rollcall and before the result is announced; and any further proceedings in reference thereto shall be after such announcement.

3. A Member, notwithstanding any other provisions of this rule, may decline to vote, in committee or on the floor, on any matter when he believes that his voting on such a matter would be a conflict of interest.

4. No request by a Senator for unanimous consent for the taking of a final vote on a specified date upon the passage of a bill or joint resolution shall be submitted to the Senate for agreement thereto until after a quorum call ordered for the purpose by the Presiding Officer, it shall be disclosed that a quorum of the Senate is present; and when a unanimous consent is thus given the same shall operate as the order of the Senate, but any unanimous consent may be revoked by another unanimous consent granted in the manner prescribed above upon one day's notice.

Resources

 * Rules of the 109th U.S. Senate

Articles

 * "Rule XII," U.S. Senate - Committee on Rules and Administration, 2005.