Which accounting method to follow ?

Hi all,

The service tax has become applicable on accrual basis since Oct. 2011 with few services being exception.  My query is whether are all those service providers who are supposed to pay service tax on accrual basis need to maintain books as per mercantile method ?  For other than companies, it is really a confusing situation because many assessee's follow cash method-particularly professionals other that covered in exceptions as per amendments in Nov/Dec 2011-but have to pay service tax on accrual basis.

Does this amendment in service tax hints at maintaining books on mercantile basis ?

Thanks