The purpose of the "Stop Subsidizing Giant Mergers Act" is to change tax rules related to large corporate mergers and acquisitions. Specifically, it aims to eliminate the tax-free treatment that certain large corporations currently enjoy when they reorganize through mergers or acquisitions. The goal is to ensure that these large corporations contribute fairly to tax revenues and to discourage excessive consolidation in the corporate sector. Key provisions of the Act include new rules for how mergers and acquisitions are taxed.