NEW YORK (CNNMoney) -- You may not know it, but you could owe Warner/Chappell Music thousands of dollars from all the birthday parties you've attended in your life.
A class action lawsuit seeks to change that.
Warner/Chappell Music claims to own the copyright to the 120-year old, 16-word song that is widely credited with being the best known piece of music in the English language. That means anyone who performs the song publicly risks a $150,000 fine if they don't agree to pay a fee to the music group.
While the company doesn't actually come after private individuals for singing the song to their 3-year-olds, it technically could. And it does demand money anytime the song is sung on a television show or movie.
Good Morning To You Productions, which is a making a documentary film about the song, filed a class action case Thursday seeking to have the song returned to the public domain. It argues the copyright on the song expired in 1921, and that it should not have been forced to pay $1,500 for the rights to use the song in its documentary.
Warner/Chappell Music is the music publishing arm of Warner Music Group, a company with $2.8 billion in annual revenue. It claims on its Web site to own the copyright to more than 1 million songs.
According to the suit, the song was written by Mildred and Patty Hill and sold to Clayton Summy in 1893 for 10% of the retail sales of the sheet music. A company that Summy founded was eventually purchased by Warner Music Group in 1998, according to the suit. It argues that if Warner/Chappell owns any copyright, it's on a very limited piano arrangement published in 1935, not on the song itself.
And it seeks to have Warner/Chappell return millions in fees it has been collecting over the years. The suit argues that Warner/Chappell collects more than $2 million a year in copyright fees on "Happy Birthday" alone.
Los Angeles-based Warner/Chappell could not be reached for comment Friday. The suit was filed in Federal Court in New York.