I'm not sure.

if you did right separate checks it might be easier to track which check was for what.

Always write the dates the child support is for. Yo will have the date paid and what date its for on th check. Never Ever Pay in cash. If you make a partial payment, date it for that month and year and stipulate on check it is a partial payment and balance owing for that month.

I it nice to see a father caring enough to make the payments up. Children have to eat:-)

Good luck in your new job

I would write out 2 checks, then you do not have to worry.

It would probably be in your best interest to send 2 checks, specifing which one is which in the memo portion of the check. that way you have documentation as to paying for both, if the problem ever comes up in court( ie, your not paying your arrearage, you were just paying ahead)
in my experience with the courts, who by the way usually screw the fathers who are actually trying to do everything that they are suppose to, pretend that you are turning in your homework at school...the more proof you have the better.