Service tax applicability for CAs

Are all services of CAs taxable? For example you may even bill a salaried assessee for IT return preparation or prepare an estimated income statement and a connected fund flow for a non-tax audit case and file his return and bill him for that.Both cases to the extent I understand may not come under accounting or auditing services etc. What should we do? Also, in the case of bank audits, sometimes you may cross the threshold with inclusion of the bank audit fee only and how could you collect service tax on the entire fee.Or should you remit what is collected and in which case there could be mismatch between taxable services and the service tax collected etc. Opinion is welcome as a whole on issues concerning CAs