Sirius XM Holdings Inc. (SIRI) saw a notable stock increase on January 05, 2026, closing at $21.10 with a +2.88% gain. This strong performance occurred alongside broad market optimism following the U.S. Treasury's finalization of a 'side-by-side' agreement with the OECD. This landmark deal exempts American companies from the Pillar Two global minimum tax framework, which analysts noted provided a significant boost to the earnings outlook for large-cap corporations and led to S&P 500 and Nasdaq Composite gains of 0.69% and 0.72% respectively.