For postgraduate research degrees, when you accept your offer, the Admissions Service will provide a research statement that you submit with your ATAS application.
For postgraduate taught degrees you will need to submit a list of the modules you will take - if you are unsure of the optional modules you will take you should include all possibilities that are currently available*.
For 'undergraduate masters' degrees you will need to submit a list of the modules you will take in the final year of the degree - if you are unsure of the optional modules you will take you should include all possibilities that are currently available*.
*please note some modules may change before you reach the final stage of your programme.