Jon Gosselin entered into a secret deal to make money outside of his TLC contract and a newly  released document has just surfaced that will sink the reality dad's case in court.

RadarOnline.com has obtained a contract that spells out a business relationship between Jon, Hailey Glassman,  lawyer Mike Heller and Michael Lohan.

And although it is unsigned, the contract led to Jon being paid for outside appearances that violated his TLC deal, says Michael Lohan.

This agreement plus  payments may be the "smoking gun" that will doom Jon in the breach of contract action brought against him by TLC.

CLICK HERE to see the secret deal memo.