A Chartered Accountant is defined as "Accountant" in the subsection 2 of Section 288 of the Income-tax Act
The Income Tax Act,1961, contains a number of provisions, which require audit for tax purposes, i.e. section 12A, 33AB, 35E, 44AB, 80HH, 80HHA, 80HHD, 80HHE, 80I, 80IA, 142(2A) etc.
So mainly the CAs do the business of accounting, book keeping and Tax Audit. They are not however having any mandatory power for any advisory services.
But as they peep into books of accounts and make all sort of dressing to accounts to provide relief to their clients, they are considered to be most trustworthy to their clients due to obvious reasons.
Now, question remains as to why M.Com, ICWA, CS etc who are qualified enough to do the same job have so far not been authorised by Income Tax to be included under the defination of accountants. One must understand LLB do not provide training for accountancy or audit. But an advocate may interpret the law of Income tax but not trained to cast the Balance Sheet.
I do not remember although that there was a landmark case in Mumbai where an Advocate has filed a case against Income Tax Commissioner as he has rejected the Tax audit report on the plea that the tax report was signed by an advocate and not a CA. The advocate lost the case on the grounds stated above. But the result could have been different if the tax audit report would have been signed by a M.Com, ICWA or CS.
So my dear friend you can do consultancy on tax planning or even casting of balance sheet but can't do tax audit.
Hope you got the key !!!