Denise Richards wants a judge to stop ex-husband Aaron Phypers from getting half of her hard-earned OnlyFans money ... and she says he missed an important deadline that could blow up in his face.

According to new legal docs, obtained by TMZ, Denise is begging a judge to deny Aaron's request for half of the $200,000-$300,000 he says she makes every month on OF.

Denise says Aaron's request should be denied because he failed to file an updated income and expense declaration with the court. She says Aaron missed a Friday deadline and hasn't filed anything as of Tuesday.

As you know ... Denise and Aaron are going through a nasty divorce and have been fighting over money ... with Aaron making his financial struggles well known.

The judge has yet to rule on Denise's request.

Stay tuned ...