It is possible to file a Motion to Modify in the original divorce court which has continuing exclusive jurisdiction in any SAPCR (Suit Affecting Parent Child Relationship) when situations change. The modification can be either to increase or decrease the amount that the paying parent is sending each month.
A good example is if a father was once making $150,000 a year and then lost his job due to the recession and was only able to find work at a $60,000 job, then he needs a domestic relations attorney to file a Motion to Modify his child support. Child support modifications such as this only make sense. If he was originally ordered to pay more than $2,000 a month when he had the higher salary, then without the modification he would still be ordered to pay that amount which would mean he would be paying more than half of his take home (net) pay.
However, it is important to realize that unless and until the modification is granted by the judge, he will still be legally required to pay the original amount. Failure to do so could result in evasive legal action being taken against him and he could actually find himself incarcerated.
On the other hand, if he was unemployed when the divorce was granted, and then two years later he landed a $100,000 a year job then the ex-wife could file a Motion to Modify Child Support to increase his monthly payments.