The "Ways and Means [Committee, H.O.R.] is empowered to hold hearings and mark-up sessions . . . During hearings, the committee hears from witnesses on the advisability of the legislation. This can include the Treasury's Assistant Secretary of Tax Policy, high-level IRS employees, tax practitioners, legal scholars, and others." (House Ways and Means, Portfolio, 100-3rd, Bloomberg BNA)
The "Senate Finance [Committee] may hold hearings and markup sessions . . ." (Senate Finance Committee, Portfolio 100-3rd, Blooomberg BNA)