The main purpose of this legislation is to change the requirements for using social security numbers when claiming the Child Tax Credit and the Earned Income Tax Credit. These credits provide financial support to families and low-income workers, and the proposed changes aim to clarify and tighten the rules around eligibility. Key provisions of the legislation include the requirement that taxpayers must include their own social security number, as well as the social security number of any qualifying child, when filing their tax returns to claim these credits.