Accounting

Historical Tax Information:

Taxation and Economic Reform in America, A Historical Archive 1781-2009

Useful IRS sites:

• IRS Tax Code, Regulations, and Official Guidance
• TaxStats
• Statistics of Income Bulletin - The SOI Bulletin is issued quarterly and "provides the earliest published annual financial statistics obtained from the various types of tax and information returns filed."
• Audit Technique Guides
• IRS Tax Forms and Instructions

Policy Information:

Tax Policy Center

Databases:

Factiva

• Federation of Tax Administrators (FTA) - State Comparisons 
• U.S. Census Bureau - State Government Tax Collections

Tax Foundation provides information on tax policies and tax rates. Data can be downloaded in PDF or as an Excel spreadsheet. Some of the most useful data includes: 

• U.S. Federal Individual Income Tax Rates History, 1913-2013
• State Individual Income Tax Rates and Brackets, 2020
• Facts and Figures Handbook 

KPMG’s Tax Rates Online

PricewaterhouseCoopers Worldwide Tax Summaries

World Development Indicators from the World Bank

• Select Country
• Select Series. [Search: tax]
• Select Time