Bill Gates tax
n. The amount of money out of the price of a new personal computer that goes to Microsoft in the form of operating system licensing fees and other charges.
Even if the court extracts a penalty on Microsoft's PC business, it will have shifted its money into new markets. Today, we pay a 'Bill Gates tax' on every PC. Tomorrow, we'll pay a similar toll to Bill for satellite systems and cable systems.
—Jesse Berst, “Life After Microsoft: What's Next and What It Means to You,” Jesse Berst's AnchorDesk, November 08, 1999
1997 (earliest)
But, in truth, the scale of Gates' personal net worth seems a poor measure of Microsoft's influence on the average computer jock. What matter to him if the market values Gates at $40 billion or even $1 trillion? Microsoft's yearly impact on his pocketbook seems a far better measure of rapaciousness.

So with a little help from our analyst friends at the New York City-based research firm IDC/LINK and PC Data of Reston, Va., the Forbes Digital Tool calculated the Bill Gates tax for 1996 (the last year all figures were available). It works out to an average of $67.25 per PC-owning household spent on Microsoft products in 1996.
—Michael Noer, “The Bill Gates,” Forbes, September 30, 1997