The Washington (DC) Post held a contest requesting new words from old words, with only one letter changed. One winner was declared in August 1998:
 
“Intaxication: euphoria at getting a refund from the IRS, which lasts until you realize it was your money to start with. (Greg Oetjen, Lorton)”
 
‘Intaxication” was the Urban Dictionary’s “Urban Word of the Day” on April 18, 2011. The word “intaxication” has been invented and re-invented many times, including at least the citations from 1933, 1960 and 1977.
     
 
10 March 1933, Riverside (CA) Daily Press,  “‘Taxoline’ Suggested as Gasoline’s Name,” pg. 3, col. 3:
“Auto-intaxication”—the state of mind which conceives only one solution for budget-balancing, namely, increasing taxes on the automobile or diverting automobile taxes. 
 
21 August 1960, Rockford (IL) Morning Star, “Jargon All Their Own” by Ed Koterba, pg. 8-A, col. 3:
But occasionally the people at the Pentagon break through with a coined word that covers a multitude of thoughts. I’m referring to their definition of the bureaucratic yen to tax everything.
 
They call it: “intaxication.”
 
Google News Archive
14 November 1977, Sarasota (FL) Herald-Tribune, “It Happened Last Night” by Earl Wilson, pg. 7-D, col. 4:
TODAY’S BEST LAUGH: United States is suffering from acute intaxication.” — Mack McGinnis.
 
Google Books
Tax Policy in the United States:
A selective bibliography with annotations, 1960-84
By Howard A. Hood; Alyne Queener Massey Law Library.; American Bar Association. Section of Taxation.
Nashville, TN: Alyne Queener Massey Law Library, Vanderbilt University
1985
Pg. 396:
The lectures included were “Taxation and Civilization in the Seventies” by Walter W. Heller, “The Role of Taxation in Meeting Social Problems” by Paul R. McDaniel, and “How Can We Kick the Intaxication Habit” by J.S. Seidman.
 
Google Books
14,000 Quips and Quotes for Speakers, Writers, Editors, Preachers, and Teachers
By E. C. McKenzie
Grand Rapids, MI: Baker Book House
1990, ©1980
Pg. 492:
Americans everywhere are now in a daze from INTAXICATION.
 
10 December 1993, Washington (DC) Times:
A reader from Cheverly called yesterday with a new word she invented that speaks for itself: “Intaxication (in-TAK-se-ka-shen) - n.”
     
Washington (DC) Post
Style Invitational
Sunday, August 2, 1998
Intaxication: euphoria at getting a refund from the IRS, which lasts until you realize it was your money to start with. (Greg Oetjen, Lorton)
 
6 March 2002, Garden City (KS) Telegram, “At Random” by Dolores Hope, pg. A4, col. 5:
Examples: Intaxication—Euphoria at getting a tax refund, which lasts until you realize it was your money to start with.
   
Urban Dictionary
intaxication
April 18, 2011 Urban Word of the Day
Euphoria at getting a tax refund, which lasts until you realize it was your money to start with.
I love feeling intaxicated!
by Oracle99 Apr 17, 2003
(...)
intaxication
euphoria at receiving a tax refund, which lasts until you realize it was your money to start with
one of the winners in the Washington Post’s Style Invitational - words altered by adding, subtracting, or changing only one letter and supplying a new definition
by dp Mar 17, 2004
   
Google Books
Internet Wisdom:
The Best of Internet E-Mail Wit and Wisdom
By Greg S. Kessler
Bloomington, IN: AuthorHouse
2007
Pg. 186:
Intaxication: Euphoria at getting a tax refund, which lasts until you realize it was your money to start with.
 
The Christian Science Monitor
Recession slang: 10 new terms for a new economy
The recession may be over, but the new slang it spawned just might be here to stay. Here are our Top 10 picks.
By Tracey D. Samuelson, Taylor Barnes, Correspondents / March 8, 2010
(...)
7. Intaxication, n. A sense of delight mingled with the perception of instant wealth that one feels upon receiving a tax refund.