If you are considering filing a modification of support action, here are a few rules:
Dependents and Filing Status if a party is married, their filing status will be Married Filing Separate per the Guidelines. The dependents are those children in your case. If Joe is married to another woman and they have a child together, that child is NOT included as a dependent in your modification action. Only the children of the parties to the action can be claimed as dependents.
10% Rule - Substantial Change of Circumstances Read 598.21C of the Code of Iowa. Section 598.21C(2)(a) sets out that there is a substantial change of circumstances if child support will vary by 10%.
10% Rule - QAD You may not apply a QAD to see if you reach the 10% level. If you reach the 10%, then you may apply a QADD.