10:34 AM PT -- TMZ Sports has now obtained the original criminal complaint filed against Tarver in Nevada in 2013 ... which shows he was charged with fraud and theft for taking out the money in 2012 and never paying it back.
According to the criminal complaint, both charges are felonies ... which means Tarver could be facing some real slammer time.
Former boxing champ Antonio Tarver never paid back $200,000 in gambling markers to the Wynn Las Vegas from a gambling binge in 2012 ... so says a lawsuit obtained by TMZ Sports.
Tarver was arrested in Florida over the weekend on a warrant out of Nevada -- the arrest documents were vague about the nature of the alleged offense.
Now, we know ... Tarver is the target of a criminal investigation for allegedly not settling several gambling markers he took at the Wynn during a 4-day gambling binge in July 2012.
According to the Wynn, Tarver took out $50k on July 24, 2012 ... another $50k on July 26 ... and $100k on July 27 ... totaling $200k.
Besides the criminal investigation, Wynn is also suing Tarver for the cash in civil court in Nevada ... the same way he went after Joe Francis when the "Girls Gone Wild" honcho flaked on a $2 MILLION marker.