"When a bill is introduced in the House, a Committee Report is published which often states the reason the bill is being proposed . . . After the bill clears the House, it is considered by the Senate. The Senate Finance Committee holds hearings and prepares a report explaining any changes made to the House bill. A Conference Committee later resolves any differences between the House and Senate versions of the bill and issues its own report . . . Committee Reports are useful tools in determining Congressional intent behind certain tax laws and helping examiners apply the law properly." (Committee Reports, IRM § 220.127.116.11.2)
Proquest Congressional (particularly its "Search by Number" function in the pull-down menu "Legislative & Executive Publications") is often the easiest platform from which to pull a Committee Report if you have the citation.
All congressional committee reports, including reports on bills that did not become law, beginning with 1990. Also sets out the legislative history of public laws as reprinted in U.S. Code Congressional and Administrative News (USCCAN) from 1948 through 1989.
Committee reports, are portions thereof, are published in the Internal Revenue Bulletin. While the IRB is freely available on the IRS website, the weekly contents of the IRB are consolidated in a permanent, indexed, Cumulative Bulletin.