Thank you for your question.
My name is XXXXX XXXXX I will do my best to help you
Since you are paying via the CSA and your daughter is doing A levels your last payment will be at the start of September
However if for any reason your daughter remains in Secondary Education (resits possibly) then the payments will continue so long as she is under 20 and in full time (more than 12 hours a week) secondary eductaion
I hope that this is of assistance - please ask if you need further details
Many thanks for that.