Levi Johnston: Deadbeat dad? Bristol Palin says pay up.

levi-johnston-bristol-palin-wire.jpg TMZ is reporting that legal documents were filed Thursday, Jan. 21 in Alaska demanding that Levi pay $1750 per month in child support to Bristol for care of their son Tripp -- retroactive to his birth in Dec. 2008.

If our math is correct... carry the 1... Levi Johnston owes Bristol Palin roughly $23,000 in child support.

Start forking over your Playgirl money, Levi.

There are two different stories as to how much Levi has paid Bristol so far. According to Bristol, Levi had paid her only $4400 over the span of Tripp's life -- made in two payments on Sept. 9, 2009 and Dec. 19, 2009.

Johnston's manager Tank is saying that Levi has paid $10,000 to her over the 13 months of Tripp's life.