How do I terminate child support when it is time

In my divorce papers it states that my child support will end at the age of 18 or after completion of high school (whichever comes first). My daughter is 18 but is still in high school because she was held back a year. She will be finished with high school June 2015 and I was wondering what I needed to do in order to stop the child support payments when she has graduated. My child support is automatically taken out of my paycheck each month by CSE.

It does not necessarily end automatically, it depends on what your order says. You may need to make a motion to terminate support, citing as a reason that the child has reached the age of majority. If it there is wage garnishment in place, I would also proactively contact Child Support Enforcement to confirm the end date.