This document updates previous FRA publications on the cost accounting methodology used by Amtrak to calculate and report route costs, Amtrak Performance Tracking (APT). The prior version of this report published in 2016, Update on the Methodology for Amtrak Cost Accounting Amtrak Performance Tracking, described Amtrak’s APT cost allocation methodology and the report appendices displayed Fiscal Year 2014 summary data from Amtrak’s accounting system. Updates to the data appendices using Fiscal Years 2017 - 2020 data were published in subsequent years. This document describes the cost allocation methodology as implemented by Amtrak at the conclusion of Fiscal Year 2021 including updates to the APT system since the 2016 report. All data within were captured in October 2021 and consist of unaudited figures from APT allocated data available at that time and do not reflect any subsequent adjustments or corrections. The figures are intended only to provide a general snapshot of the relative size of Amtrak’s business and may not directly align with other published Amtrak reports, based on differences in reporting methodologies. The data described in the report and the appendices should be viewed holistically and do not necessarily account for changes within the APT structure over time.