This variable provides the application number (k = 1 to 4) that matches with the date of filing for benefits. This variable pertains to mbr_ssdi_deny_dof. The MBR has information on dates of filing for most recent accepted OASDI application and most recent rejected OASDI application. If one of the four SSDI applications included in the SSB aligns with the individual's SSDI history and the timing of an SSDI application, mbr_ssdi_ddof_app will indicate which application.