If you need an earlier version of the Internal Revenue Code (26 USC) or Internal Revenue Service’s Regulations:
Internal Revenue Code KF 6277.515 .I57
For each year starting in 1954, this set of books captures the text of the Internal Revenue Code (IRC) on last day of the previous year’s Congressional session. For instance, the the 2012 volumes contain the text of the IR. as amended through December 30, 2010 at the end of the first session of the 112th Congress.
Federal Tax Regulations KF 6277.52.A19F42
For each year starting in 1954 this set of books captures the text of the Tax regulations as amended through December 31st of the prior year. For instance, the 2012 volumes contain the text of the I.R.S. regulations in effect on December 31, 2011.