Janet D said:
If you are self studying then you can choose which one to take if you look on the ICB website.
I have just passed the 2017/18 self assessment exam in the nick of time because the exam expires at the end of this month.
I would reccomend taking the 2018/19 exam as a lot of the tax thresholds change each year.
THEREFORE YOU SHOULD REALLY BE DOING THE 20/21 STUDY MATERIAL (IF THERE IS), AS THAT IS THE CURRENT YEAR WE ARE ACTUALLY IN.
WHATEVER YOU DO, ENJOY & LOTS OF LUCK!