This bill eliminates the existing de minimis treatment under the Tariff Act of 1930, which previously allowed for the duty-free entry of low-value shipments into the United States. The termination of this provision takes effect immediately for articles originating in China, with a brief exception for goods already in transit. For articles from all other countries, the change will apply 120 days after the bill's enactment. The legislation mandates that the Secretary of the Treasury undertake a rulemaking process within 120 days to implement these changes. This process must establish new entry procedures and enhanced data requirements, including the provision of 10-digit Harmonized Tariff Schedule (HTS) heading numbers for informal entries, to ensure effective enforcement and accurate collection of duties and fees. Additionally, the rulemaking must develop regulations and guidance for penalties to deter unlawful or fraudulent activity and ensure reasonable care in documentation. Finally, the Secretary, in consultation with the Postmaster General, must determine appropriate fees and procedures for international postal shipments to ensure consistency with other entry methods.