The Commenced PMN Case Number Concordance or Cross-Reference file contains PMN Case Numbers cross-referenced to Chemical Abstracts (CAS) Registry Numbers and Environmental Protection Agency (EPA) Accession Numbers assigned to the substances described in PMN Notices of Commencement of Manufacture or Import. If no claim of confidentiality for the substance identity was made when the Notice of Commencement was submitted, or if the submitter subsequently withdrew the claim of confiddEntIality for the substance identity, then the substance will have a CAS Registry Number. If Confidentiality was claimed for the substance in the Notice of Commencement and there has been no change to that claim, then the substance will have an EPA Accession Number, which is a unique five or six-digit number EPA assigns to each confidential substance added to the Toxic Substances Control Act (TSCA) Inventory. The file is in Case Number order. Associated with each Case Number is one or more CAS Registry Numbers or EPA Accession Numbers. Typically there will be only one of these numbers associated with a Case Number, however where more than one unique substance is encompassed by a single commenced PMN, the appropriate CAS Registry Number or EPA Accession Number for each substance will be included in the workunit for that particular Case number. Each issue of the file is cummulative.