You should let your employer know that you're unwell and cannot sit your assessment in the first instance.
If you know you wont be sitting the assessment, email us at scheduling@icas.com, copying in your employer, and we will cancel the enrolment.
ICAS operates a ‘fit to sit’ policy, so by starting the assessment, you are declaring that you are both mentally and physically capable of sitting the assessment. If you do not start the assessment, it will not be counted as an attempt.