
Brian Emmett won the Oracle Space Sweepstakes competition to win a flight into orbit with Space Adventures Ltd, which organises trips to the International Space Station.
The Oracle developer won the prize after answering a series of questions about Oracle's code and development strategies.
Emmett was "over the moon" as he is a space enthusiast; he has attended space camp during a holiday and seen many shuttle launches.
But under US tax laws prizes count towards taxable income and he worked out that the cost of the trip would leave him owing US$25,000 in back taxes.
"After some strenuous hand-wringing and lots of talking with the family tax attorney, the only option was forfeiture of the prize," he wrote in his Eminent Brain blog.
"Going US$25,000 into the hole on the promise that I might, at some distant point in the future, be able to fulfill a childhood (okay, adult) fantasy when weighed against the immediate realities of my life didn't seem like good math to me."
Oracle did provide a US$35,000 cheque to offset some of the costs but the value of the ride was US$138,000 for tax purposes.
"This was probably one of the toughest decisions I'd made in my life so far. Turning down the ability to realise a childhood dream when it's so close you can touch it is really impossible to put into words."
Oracle is now choosing another winner for the prize. Winners from Asia and Europe will also be going on the trip into orbit.