Why are the tests and re-sits only available in a three-week window?

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 four 3-week windows each year, one each quarter, for you to select. If you need to re-sit the test, this must be done within the same 3-week window as your original test. Your chosen training provider will be able to advise on which dates they are running the test.