Child's mom insists that I always drop off check. She plays no part in picking it up and sometimes won't ansewer the phone just to make payment so called late. She even filked with the court recently because I was served once again. She has support cases in two towns against me. Who knows ntrhe rules because as a dad I no answers except make your payments.

Well first always keep your receipt (cleared check records from your bank). Next, if you are uncomfortable making payments directly to her ask the court if you can pay through them. I know lots of people that do it this way. In order to find out if you can do that on your own or if you have to have it ordered that way call the child support office you should have a case worker there that will know how yours is ordered and they should be able to tell you but may require you to go in to talk to them for privacy liability reasons.