Find federal tax rates for past years online through a number of websites, including the Tax Foundation. The IRS also provides historical data tables directly on its website, but the IRS tables only include the highest and lowest tax brackets for individual taxpayers.
Tax rate listings are available for download on the Tax Foundation's website in both Excel and PDF formats, dating as far back as 1862. The organization's website presents marginal tax rates along with the corresponding tax brackets, which have also shifted over time. The tax rates provided are for each type of individual taxpayer, including married filing jointly, married filing separate, single and head of household. Because of the length of time covered, the Tax Foundation presents tax brackets in both nominal and inflation-adjusted form, with the latter adjusted according to the Consumer Price Index.
The Tax Foundation website also provides past corporate tax rates along with the corresponding income brackets. These rates date back as far as 1909. The Tax Foundation also makes available past state-level tax rates for both individuals and corporations for as far back as 2000, including any applicable tax brackets and relevant notes on issues such as pending changes and special tax structures.