A few initial thoughts on getting started with this kind of research.
First, in some ways this is like any other research. A reminder of the Legal Research Mini-Playbook, which outlines basic strategy advice on doing legal research. The most basic principles there are use secondary sources early and often and when looking at primary materials, such as statutes and regulations, make sure you use annotated versions of them, which are available on Lexis and Westlaw.
Second, also understand that tax research is particularly complicated, in part because there are additional primary sources that are unique, such as Revenue Rulings and Private Letter Rulings. In complicated areas of legal research, using legal research guides, which are designed to give you the lay of the land and some background, can be very helpful.
Third, tax research is an area where even citations can become confusing. For example, citations to the "Internal Revenue Code" or IRC are the equivalent of 26 U.S.C - so IRC § 501(c)(3) is the same as 26 U.S.C. § 501(c)(3) and, like with other statutory research, we want to look it up in an annotated form (the Bluebook allows this at Rule 12.9.1. Similarly references to Treasury Regulations are the equivalent of 26 C.F.R. so Treas. Reg § 1.501(c)(3)-1 or even just Reg. § 1.501(c)(3)-1 is the same thing as 26 C.F.R. § 1.501(c)(3)-1.
Finally, please do not hesitate to reach out for assistance at either douglas.cox@law.cuny.edu or legal.research@law.cuny.edu. The type of research you will be doing will be a great exercise in solidifying your knowledge of legal research, so we encourage you to reach out to get the most out of it.
Legal Research Guides
Getting Started - Tax Research - Federal (Georgetown)
Federal Tax Research - Outline and Guide (NYU)
Federal Tax Research (Brooklyn Law)
Non-Profit Organizations Research Guide (Georgetown)
Secondary Sources
Taxation of Exempt Organizations (Westlaw)
Nonprofit Organizations: Law & Taxation (Westlaw)
Representing Nonprofit Organizations (Westlaw)
LexisNexis Internal Revenue Code Explanations (Lexis)
The Law of Tax-Exempt Organizations (Lexis)
Planning Tax-Exempt Organizations (Lexis)
Primary Materials
Tax Practice Area (Westlaw)
Tax Law (Lexis Advance)
Annotated Internal Revenue Code
Internal Revenue Code & 26 USCA § 501 (Westlaw)
Internal Revenue Code & 26 USCS § 501 (Lexis)
Annotated Treasury Regulations
Treasury Regulations (see, e.g., § 1.501(c)(3))(Westlaw)
Treasury Regulations (Lexis)
Revenue Rulings & Private Letter Rulings
Tax Administrative Decisions & Guidance (Westlaw)
Tax Administrative Materials (Lexis)