Frantic Katie Holmes is racing to reinvent herself as her kid with ex Tom Cruise turns 18 next month — meaning an end to the hefty $400,000 she gets every year in child support!

For over a decade, the former Dawson’s Creek cutie, 45, lived high on the hog, thanks to the plush payments from 61-year-old Tom, but that financial cushion is about to lose its stuffing — which is why sources say Katie is on the prowl for acting work!

“For years, Katie’s enjoyed a lavish lifestyle, thanks to Tom’s consistent support,” a source exclusively tells In Touch. “But as their child nears adulthood, both mother and daughter are facing an uncertain future. It’s a terrifying prospect — going from an amazing standard of living to a question mark overnight!”

Although Holmes has earned her own money since leaving Tom in 2012, sources say it’s pennies compared to what she gets in child support.

“Dawson’s Creek royalties don’t hold a candle to what Mission: Impossible generates!” the insider adds.

“She’s actively looking for roles and is eager to throw herself back into the industry full-time. And don’t forget the non-disclosure agreement she signed — it’s set to expire, too. If things get tough, Katie could cash in by penning a tell-all book!”