; and (B) for necessary expenses for tax enforcement activities in order to determine and collect owed taxes, to conduct criminal investigations, and to enforce criminal statutes related to violations of internal revenue laws and other financial crimes. (2) Auditing levels The minimum levels described in this paragraph are as follows: (A) Fifty percent of individuals or joint returns with gross income of not less than $100,000,000. (B) Thirty-five percent of individuals or joint returns with gross income of not less than $10,000,000 and less than $100,000,000. (C) Twenty percent of individuals or joint returns with gross income of not less than $5,000,000 and less than $10,000,000. (D) Ten percent of individuals or joint returns with gross income of not less than $1,000,000 and less than $5,000,000. (E) Ninety percent of corporations with gross income of not less than $20,000,000,000. (F) Fifty percent of corporations with gross income of more than $1,000,000,000 and less than $20,000,000,000. (b) Improving technology infrastructure There is appropriated for each of fiscal years 2021 through 2030, for efforts collecting and protecting taxpayer information, reducing tax-related theft and fraud, and modernizing the technology infrastructure of the Internal Revenue Service— (1) $3,800,000,000 for an additional amount for the Department of the Treasury—Internal Revenue Service—Operations Support account; and (2) $500,000,000 for an additional amount for the Department of the Treasury—Internal Revenue Service—Business Systems Modernization account. (c) Enhancing taxpayer services There is appropriated $2,500,000,000 for an additional amount for the Department of the Treasury—Internal Revenue Service—Taxpayer Services account, for each of fiscal years 2021 through 2030, for the salaries and expenses of additional staff to achieve adequate staffing levels to provide taxpayer services, including pre-filing assistance and education as well as filing and account services.