Although there is no requirement to notify your employer that you are engaging in protected industrial action on the day (as they will already have been notified by the AFPA), it is advisable to do so. Union members who have previously taken action reported it was easier to take protected industrial action once their employer knew. It also assists with job planning, putting the obligation back on the employer to manage the effects of the protected industrial action. 

If you are asked directly whether you have taken industrial action or are presently imposing a ban, you should answer the question.