The main purpose of this legislation is to amend the Social Security Act and the Internal Revenue Code to enhance funding for the Federal Hospital Insurance Trust Fund, which supports Medicare. It aims to include the net investment income tax as a source of revenue for this fund and to modify how this tax is applied, particularly for high-income individuals. Key provisions of the legislation include the following changes: First, it adds the net investment income tax to the sources of revenue for the Hospital Insurance Trust Fund, which is crucial for financing Medicare.