If you are a student taking a course that requires a re-sit, you will have to wait 24 months before you can try again. This will allow time for the exam system to be reviewed by the DfE.
If you don’t pass the first time, you can retake the exam at any time within the 24 months period. So, if you were 17 years old in June 2018, you will have until November 2019 to take the exam and receive the results.
If you want to know exactly how long it will be until you can take the exam again, just follow the link above. For more information on the resit rule AAT Exam Centre and what it means, check out the official UK CELTA website. The rules have changed so that you can now take the exams twice within a 24 months period.
Before you took the CELTA exam, you could take it multiple times. Once you passed, you could retake it any number of times. But, starting in 2012, students and apprentices aged 16 and older were allowed to take the CELTA exam only once, within a two year period.
The purpose of this rule was to stop people from ‘gaming’ the system and taking the exam several times in a short space of time, to get a higher score.