Thank you for the answer.
My conclusion is that the PRSI contribution is 4% of the income or €500, whichever is greater - if earnings are more than €5,000 per annum (with Subclass S0 for weekly income below €500 and Suclasss S1 for weekly income above €500).
If earnings per annum are below €5,000, there is no PRSI contribution liability. However, when filling in the P35L on ROS, the system doesn't accept €0 as the PRSI contribution. Is there something I've missed?
Many thanks.