{"abstract":"This document contains final regulations defining last known address in relation to the mailing of notices of deficiency and other notices, statements, and documents sent to a taxpayer's last known address. The final regulations affect taxpayers who receive notices of deficiency and other notices, statements, and documents sent to taxpayers' last known addresses.","action":"Final and temporary regulations.","agencies":[{"raw_name":"DEPARTMENT OF THE TREASURY","name":"Treasury Department","id":497,"url":"https://www.federalregister.gov/agencies/treasury-department","json_url":"https://www.federalregister.gov/api/v1/agencies/497","parent_id":null,"slug":"treasury-department"},{"raw_name":"Internal Revenue Service","name":"Internal Revenue Service","id":254,"url":"https://www.federalregister.gov/agencies/internal-revenue-service","json_url":"https://www.federalregister.gov/api/v1/agencies/254","parent_id":497,"slug":"internal-revenue-service"}],"body_html_url":"https://www.federalregister.gov/documents/full_text/html/2001/01/12/01-623.html","cfr_references":[{"chapter":null,"citation_url":null,"part":1,"title":26},{"chapter":null,"citation_url":null,"part":301,"title":26}],"citation":"66 FR 2817","comment_url":null,"comments_close_on":null,"correction_of":null,"corrections":[],"dates":"Effective date: These regulations are effective January 12, 2001.","disposition_notes":null,"docket_ids":["TD 8939"],"dockets":[],"document_number":"01-623","effective_on":"2001-01-12","end_page":2821,"executive_order_notes":null,"executive_order_number":null,"full_text_xml_url":"https://www.federalregister.gov/documents/full_text/xml/2001/01/12/01-623.xml","html_url":"https://www.federalregister.gov/documents/2001/01/12/01-623/definition-of-last-known-address","images":{},"images_metadata":{},"json_url":"https://www.federalregister.gov/api/v1/documents/01-623?publication_date=2001-01-12","mods_url":"https://www.govinfo.gov/metadata/granule/FR-2001-01-12/01-623/mods.xml","not_received_for_publication":null,"page_length":5,"page_views":{"count":681,"last_updated":"2026-10-22 16:15:06 -0400"},"pdf_url":"https://www.govinfo.gov/content/pkg/FR-2001-01-12/pdf/01-623.pdf","presidential_document_number":null,"proclamation_number":null,"public_inspection_pdf_url":null,"publication_date":"2001-01-12","raw_text_url":"https://www.federalregister.gov/documents/full_text/text/2001/01/12/01-623.txt","regulation_id_number_info":{"1545-AX13":{"issue":"200010","html_url":"https://www.federalregister.gov/regulations/1545-AX13/definition-of-last-known-address","title":"Definition of Last Known Address","xml_url":"http://www.reginfo.gov/public/do/eAgendaViewRule?pubId=200010&RIN=1545-AX13&operation=OPERATION_EXPORT_XML","priority_category":"Substantive, Nonsignificant"}},"regulation_id_numbers":["1545-AX13"],"regulations_dot_gov_info":{"checked_regulationsdotgov_at":"2011-11-12T03:58:48Z"},"regulations_dot_gov_url":null,"significant":false,"signing_date":null,"start_page":2817,"subtype":null,"title":"Definition of Last Known Address","toc_doc":"Last known address; definition","toc_subject":"Income taxes, etc.:","topics":["Employment taxes","Estate taxes","Excise taxes","Gift taxes","Income taxes","Penalties","Reporting and recordkeeping requirements"],"type":"Rule","volume":66}