This document is about the layout and variables of the March 2020 CPS Auxiliary data file. It provides a detailed breakdown of the fixed format file, including the column, variable name, start position, length, and description for each field. The file contains identification information from the original March supplemental file, as well as recoded insurance variables and imputed information on the sources of employer sponsored insurance. This file can be used in conjunction with the full person level CPS file by matching the PH-SEQ and A-LINENO variables.