He was President of the American College of Tax Counsel (ACTC); was Chair of the 4,000+ member Taxation Section of the State Bar of California from 1999 to 2000;[3] the longtime Chair of the UCLA Extension Annual Tax Controversy Institute; and served as vice-chair, Administration, for the 12,000+ member Taxation Section of the American Bar Association.

During his confirmation hearing before the Senate Finance Committee on June 28, 2018, Rettig "told lawmakers he would ensure that the agency is 'impartial and non-biased from top to bottom' and follows the law.

In May 2018, four months prior to Rettig's confirmation as commissioner, the IRS planned to cut 2,200 employees as part of its FY 2019 budget.

[23]) On May 21, 2019, Lloyd Doggett, a Member of the U.S. House of Representatives from Texas, called for Rettig to be jailed for not turning over then-President Donald Trump's tax returns.

[27] In response to questioning by the U.S. Senate's Finance Committee, Rettig said that he would launch an investigation into the potential source of the ProPublica article detailing the billionaires' tax returns.

[28] The piece also critiqued the work of what Rettig called a "wealth squad" within the IRS that targeted high-income individuals for audits.

[29] At his nomination, Rettig received criticism "for failing to disclose that he had a stake in two rental units in Hawaii at a Trump-branded hotel."

He co-founded the UCLA Extension Vets Count Scholarship Fund, designed to provide scholarships for active duty and retired military personnel who are working to realize their career goals in tax, accounting, wealth management, and other areas of the financial services industry as well as basic coursework for personal growth in budgeting, financial literacy, and investing.