Contact the agency that collects child support (the family court should be able to point you in that direction) and see if you need a court order to collect through them, either him paying them the child support (this way, if he's late it's not just a he said she said situation) or a wage garnishment.

If you don't, then sign up and let them handle it. It's going to be about a week delay, anyway. But your ex doesn't get to play this game with you to annoy you.