First check to see if anyone else has already compiled a legislative history of the act you are researching. Resources that will help you do this are:
1. U.S. Federal Legislative History Library (available from Hein)
2. Taxation and Economic Reform in America Parts I & II (available from Hein)
The most comprehensive selection of tax legislative history materials. The database includes the full text of dozens of tax books, economic reform books, tax legislative histories, economic reform legislative histories, and the Internal Revenue Acts from 1909 to 1950. All content is image-based in PDF format, and appears just as in the original print copy of the work.
3. Joint Committee on Taxation General Explanation (known as Bluebooks)
After the enactment of significant tax code provisions, the JCT publishes the General Explanation which provides useful explanations of newly enacted tax acts.
4. ProQuest Legislative Insight
Legislative Insight provides compiled histories with full text PDFs and tools to facilitate research into the legislative histories of U.S. statutes.
5. Westlaw Federal Tax Legislative History database (login to Westlaw, search for "Federal Tax Legislative History)
Congressional committee reports setting out the legislative history of tax-related public laws as reprinted in U.S. Code Congressional and Administrative News from 1948 through 1989. From 1990 forward, the database contains all congressional committee reports, including reports on bills that did not become law. Presidential signing statements, issued at the time the president signed a bill into law, are also included.
6. Lexis Tax (Login to Lexis+, click window and choose "Lexis Tax")
Access to Federal Code Reporter, Statutes, Regulations, news, and cases, all in one spot.
Lexis+ has a few really great databases for Tax Legislative History. Here are a few of the most helpful:
1. Lexis Tax (Login to Lexis+, click the window icon and choose "Lexis Tax")
Search the Federal Code Reporter by clicking on "Legislative Histories" and finding the IRC section you want to research.
2. Tax Legislative Histories, Combined (login to Lexis+, type the name into search bar)
This file contains selected House, Senate, and Conference Committee Bills and Reports, as well as Public Laws, of passed legislation which deal with Title 26. Documents include: - Public Laws from 1954 to 2004 (Please see source USCS - Public Law for full text Public Laws from September 9, 1988 through current.) - Joint Committee Prints from 1981 (Selected) to current - Joint Committee Bluebooks from 1976 to current - House Ways & Means Committee Bills and Reports from 1954 - 1998 - Senate Finance Committee Bills & Reports from 1954-1998 - House-Senate Conference Committee Bills and Reports from 1954-1998 - Selected Proposed Tax and Pension Legislation from 1954-1998 Post-1998 Committee Reports can be found in the source: Committee Reports (CMTRPT). Post-1998 Senate and House Bills can be found in the sources: Federal Bill Text Combined Archive and Congressional Full Text Bills - Current Congress