Prorated Child Support

My daughter turns 18 on July 11. Should I just pay the eleven days worth of child support for that month?

The full payment for July should be made.

Hi there, I asked this question several years ago, and I was told we could pro-rate the last check. Is this requirement in the guidelines anywhere?
Thanks!

No, the law simply states that support will end when the child turns 18 (or graduates from high school) which ever is later.