In this action, the U.S. Environmental Protection Agency (EPA) is finalizing technical revisions and clarifications for the national emission standards for hazardous air pollutants (NESHAP) for MSW Landfills established in the March 26, 2020, final rule. This final rule also amends the MSW Landfills NSPS at 40 CFR part 60, subpart XXX, to clarify and align the timing of compliance for certain requirements involving installation of a gas collection and control system (GCCS) under related MSW landfill rules.