EXCLUSIVEAnswer: Kelis paying taxes in 2004.
Question: What is something that did NOT happen?
According to documents filed in May by Uncle Sam, Kelis did not pay federal income taxes 9 years ago ... to the tune of $134,931.59.
As TMZ first reported, the singer also skipped out on her NY state taxes in 2004 and 2010 ... as well as 2 years of CA state and federal taxes -- add on the new lien, and her total debt comes to $741,027.59.
In related news -- Kelis recently sold a condo in NYC for about $2.2 million ... so she might have the scratch to settle up with the taxman.
Calls to Kelis' camp have not been returned.