Monica, Sister Mary Ann may not have to worry about paying taxes---but a member of her religious community [Treasurer] DOES.  Salaries and stipends, which are paid by check are sent, not to the individual religious, but to the financial account of the congregation/order.  The Treasurer needs to know from individual religious what their salary/stipend is from year to year.  Income tax must be paid for each member who brings in anything.  

Religious also receive Medicare.