My son just turned 18, I want to see if I can get an order for back child support. In 2000 I wrote a letter, non-noterized stating (exact words) "Let it be known that I waive child support services and arrears due from father, concerning child, due to moving out of the country for a period of three years." Help! I'm so confused about the "3 yrs" part. It was meant as suspending it while we were out of the contry, not for good entirely. However, 11 years later hear I am. I often inquired but because of military obligations and moves the subject often paled in comparison. Also, The original order was in NY we currently live in NC and the father is in PA. What state would the laws and statues be enforced?

First your letter even if notarized has no real legal value, the other side could use it as a partial defense, but since you can't give up your rights,
Next if there was an original court order, it is still in place, and you merely need to go back to that court for enforcement.