grants program for tax return preparation assistance, and of which not less than $206,000,000 shall be available for operating expenses of the Taxpayer Advocate Service: Provided , That of the amounts made available for the Taxpayer Advocate Service, not less than $5,500,000 shall be for identity theft and refund fraud casework. enforcement For necessary expenses for tax enforcement activities of the Internal Revenue Service to determine and collect owed taxes, to provide legal and litigation support, to conduct criminal investigations, to enforce criminal statutes related to violations of internal revenue laws and other financial crimes, to purchase and hire passenger motor vehicles ( 31 U.S.C. 1343(b) ), and to provide other services as authorized by 5 U.S.C. 3109 , at such rates as may be determined by the Commissioner, $4,860,000,000, of which not to exceed $50,000,000 shall remain available until September 30, 2020, and of which not less than $60,257,000 shall be for the Interagency Crime and Drug Enforcement program. operations support For necessary expenses of the Internal Revenue Service to support taxpayer services and enforcement programs, including rent payments