2021 Document 6209 is a reference guide which contains ADP and IDRS data relative to various components of the IRS. It is updated annually. Table of Contents PDF Section 1, Glossary PDF Section 2, Tax Returns and Forms PDF Section 3, Tax Return Information PDF Section 4, Document Locator Number PDF Section 5, Debtor Master File PDF Section 6, Initiating and Monitoring Refund Check Tracing Action PDF Section 7, Automated Non-Master File PDF Section 8A, Master File Codes - Transaction, MF and IDRS Collection Status, Freeze and IDRS Status 48, Restrictive and Filing Requirements PDF Section 8B, Master File Codes - Unpostable and Resequence PDF Section 8C, Master File Codes - Source, Reason, Hold, Priority, Item Adjustment & Credit Reference, NMF Abstract, Underreporter, Process, No Merge Reason, EP PDF Section 9, Notices and Notice Codes PDF Section 10, Penalty and Interest Provisions PDF Section 11, Collection PDF Section 12, Examination PDF Section 13, Appeals and TE/GE PDF Section 14, Integrated Data Retrieval System (IDRS) PDF Section 15, Other Systems CADE, CADE 2, SCRIPTS, CFOL and FTD PDF Section 16, Julian Date, Cycle and Notice Calendars PDF Appendix PDF