If your salary is ₹30 lakhs, it is not possible for you to have a NIL tax payable or no tax liability even if you claim all the allowances available under Sections 10 and all the Schedule VI A deductions. You may minimize your tax liability based on the eligible allowances and deductions applicable to your specific case but it may not be possible to have a NIL tax liability with an income of ₹30 lakhs per annum.