Flo Rida vs. Florida -- Baby Mama Gets Backup in Child Support War

Flo Rida's baby mama is demanding the rapper fork over some dough for his kid ... the very same kid Flo adamantly DENIED fathering -- but now we know the truth.

The Florida Dept. of Revenue filed legal docs in connection with Gloria Holloway's request for child support from Flo -- real name Tramar Dillard -- for Gloria's two-year-old son.

As TMZ previously reported, Flo denied knocking up Gloria ... and even claimed he took a paternity test that came back negative -- but according to the new docs, the court has ALREADY established paternity.

Here's why ... when child support requests come through the state's Dept. of Revenue -- it usually means no one's disputing it. Translation: Looks like Flo's the daddy.

Now the state of FL wants Flo to hand over his financials so it can determine how much he owes.

We reached out to Flo ... but no word back yet.