When seeking a divorce, do you have to ask for child support or are you able to waive your right to support?

My husband and I are disagreeing about this issue.

He has custody of his 8 year old son, in his divorce papers it states that his ex is to pay $100 a month in support which she has not been doing (they have been divorced for 3 years). My husband is not trying to enforce the child support order saying that he doesn't need her help, it would do no good, she can't afford it anyway, and that the only reason he had it put in the papers was because he had to. I told him he could have waived his right to support just like you can waive your rights to spousal support but he disagrees.

What are your opinions on this? (We live in SC if that makes a difference)

If it was ordered it should be paid. If not paid she is in contempt of the court order.

I do know of one case where Child Support was not ordered. The parent filing for divorce and custody specifically asked for, and was granted, no child support. This is extremely rare though.