Yes, potentially your wages could be garnished, or a bank account garnished (the money taken from the account). Your ex-husband cannot due this automatically, but would have to go to court for these remedies. While its not terribly expensive or difficult to do this things when someone doesn't pay a lawful debt or obligation, there is some cost and effort involved, so it's not a given he would do this for $200. He does, however, have the right to do so. Also, if you default on this debt, it could possibly damage your credit rating, which could ultimately cost you more than the $200. On the balance, it probably is in your interest to pay the money.