This is a matter open to agreement but if no agreement is reached then the duration of child maintenance payments will depend upon whether the payments are made through the CSA. If they are, the maintenance will last until the child reaches the age of 16, or if they are still in full-time education, until they reach the age of 19. If the payments are made in accordance with a court order then their duration will depend upon the terms of the order.
A typical court order may specify that the maintenance shall continue until the child reaches the age of 18 years or ceases full-time secondary (or tertiary) education, whichever shall be the later.