The model-turned-actress has been dating Carrey for four years and the couple has been living together since 2008.
But the former Playboy model insists she has no plans to exchange vows with The Mask star because she already considers herself "married" - and she would only ever rethink her decision for financial purposes.
She says, "I had a dream last night that I left him at the altar because I don't want to get married. We are married, we don't need a piece of paper. Maybe one day (we'll marry), when I'm 80 and I need a tax write off!"
McCarthy was previously married to actor/director John Mallory Asher, with whom she has a son, Evan. The couple filed for divorce in 2005 after six years as husband and wife.
Carrey is a double divorcee - he split from first wife Melissa Womer in 1995 after eight years of marriage, and went on to wed his Dumb and Dumber co-star Lauren Holly in 1996. They split less than a year later.