Sign & seal that winning ticket

HOLD the champagne.

The first thing you should do if you win the big one? Scrawl your John Hancock on the back of the ticket — then keep it quiet.

“Sign the ticket. Because keep in mind that little slip of paper is a billion-dollar bill — imagine that,” Mega Millions lead director Gordon Medenica said Monday on NBC’s “Today.” “So you want to secure it and also be calm.” With the estimated $904,900,000 lump sum, a single winner from New York City stands to collect $572,837,896 free and clear after forking over federal, state and local taxes.

But don’t expect to revel in the billion-dollar bonanza in private.

The state Gaming Commission reserves the right to use the winner’s name, hometown and photograph for publicity and may require them to appear at a press conference.

Experts also say that claiming the windfall through a limited liability company or trust is futile, and that, eventually, your name will become public.

But Andrew Plasse, an attorney for a $5 million scratch-off winner in The Bronx who unsuccessfully sued to keep his name secret, said anonymity is worth fighting for — if your safety is in jeopardy.

“We argued that the public policy of the state is to publish the name so they can get more people to buy tickets,” Plasse said. “[But] there’s a health factor, the safety factor of the individual that outweighs public policy.”