My net income is down this year with the recession. How do they determine what income to use for child support in Texas?

Child support in Texas is a mathematical formula based mainly on your income. The state guidelines apply a set percentage based on the number of children you have (20% for one child, 25% for two children, etc) to your net resources. Net resources isn't exactly the net you see on your paycheck, but a net calculated on factors set out in the Texas Family Code. Because child support is a backwards-looking calculation, the courts usually look at the last two years of income. If there has been a significant change over the last two years, you can argue for the court not to do that and to only look at the current state of affairs. A court may also vary the child support (up or down) based on various equitable factors such as the needs of the child, the situation with one of the parents, visitation schedules, etc. In some states, both parents income is taken into account, but in Texas usually only the parent paying the child support will have his (or her) income used to determine the amount due.