Eddie Cibrian has reportedly overpaid Brandi Glanville more than $100k in spousal support, and he's fighting to get it back.

His reps said that Brandi is a liar in claiming on Twitter earlier this week that Eddie was suing her for child support.

Brandi tweeted, "...Mr. fancy new cars & house man is asking ME for child support," and Eddie's reps said "It's a complete lie."

The former couple hired a law firm to help figure out who owes what, and a full audit showed that Eddie overpaid Brandi’s alimony by $114,738.

As for how Eddie expects Brandi to pay him back ... the lawyer's letter claims that it will be subtracted from her share of his retirement accounts.

Source: TMZ