An MRR file is used to submit a unique set of mark/recapture/recovery PIT tag data. The file name is treated as a key and used to identify the distinct set of records contained within the file. The data submitted in an MRR file can be corrected by submitting an edited version of the file as a correction. The edited file must have the same file name and contain all records, not just those that are being corrected.

There are two MRR file formats accepted for loading into PTAGIS: the P4 format, which has been accepted since 2016, and the P5 format, which has been accepted since March 2025. The P3 file format was the previously accepted from 2002 until January 1, 2019.

Prior to 2002, several different file formats were accepted, primarily those created by PTAGIS software PITTag and PITTag2. See the historic specification documents available in the change log for more information about those file formats.