This rule finalizes amendments to the General Provisions that apply to National Emission Standards for Hazardous Air Pollutants (NESHAP). These amendments implement the plain language reading of the "major source" and "area source" definitions of section 112 of the Clean Air Act (CAA) and provide that a major source can be reclassified to area source status at any time upon reducing its potential to emit (PTE) hazardous air pollutants (HAP) to below the major source thresholds (MST) of 10 tons per year (tpy) of any single HAP and 25 tpy of any combination of HAP. This rule also finalizes amendments to clarify the compliance dates, notification, and recordkeeping requirements that apply to sources choosing to reclassify to area source status and to sources that revert back to major source status, including a requirement for electronic notification.