The main purpose of this legislation is to change the rules regarding who can claim the child tax credit. Specifically, it aims to require individuals to provide a social security number in order to qualify for this tax benefit. The goal is to ensure that only those who are legally eligible, particularly U.S. citizens and certain lawful residents, can receive the credit. Key provisions of the legislation include a requirement for taxpayers to include their own social security number, as well as the social security number of any qualifying child, when filing their tax returns.