Because of robust governance and checks around the test and who is undertaking it, it is only available over strict and monitored timescales. There will be a number of scheduled windows each year for you to select.
If you need to re-sit the test, this must be done within the same window as your original test, so we recommend booking your test as early as possible within the assessment window, in case you need to re-sit within that same period.
Your chosen training provider will be able to advise on which dates they are running the test.