Will a notarized letter stating custodial parent will not file or collect child support from non-custodial parent work?

It is certainly evidence that could be presented to a Court in support of this theory. However, it is unlikely that a Court would agree that a non - custodial parent should not be paying any money to the custodial parent to help support their child. You should consult with a local family law attorney in regards to this matter as soon as possible.

Depending on the Judge and what the letter specifically states, this letter will be strong evidence against any claim for support. However, you should consult with an attorney to make sure all potential claims are resolved now and in the future.

No, a parent cannot refuse to receive child support.

You are under an obligation to care for your children. What will hold up in court is your ex not contacting CSSD to help her collect child support. But parents are supposed to support their children so there is a chance that this may not hold up in court. I suggest you hire an attorney to make sure that this is the best way to not pay child support.

Not in Colorado if your ex changes her mind. Courts generally will not approve agreements to waive child support because child support is a right of the child - not the parents. As long as no one complains, the court won't get involved so it doesn't make much difference whether there is anything in writing; notarizing only provides verification that someone signed - nothing else. If, in the future, she chooses to file for child support the agreement might be enforced by the court as to past support so that no retroactive awards are required, but the agreement as to future support will be considered unenforceable.