1) All reasonable expenses incurred in connection with the earning of your professional income will be allowed as deduction in computing your taxable income. Your professional income will be assessed under the head : Income from Business/Profession. You will be able to claim deduction on account of depreciation on your assets employed in your profession, such as Laptops, Mobile, vehicle. The other expenses like travelling and conveyance to the extent they are not reimbursed by your firm/client can also be claimed. In addition regular expenses such as your expenditure on books, vehicle maintenance and communication expenses can also be claimed.
2) Your professional income will be subject to TDS @ 10%. After you claim the reasonable expenses as mentioned above and deductions available under Chapter VIA of the IT Act like 80C,you may not have taxable income upto your earnings upto Rs 5 Lakhs. Once your total income after all expenses and deductions exceed Rs. 5 Lakhs, you will get into 20% bracket. However you would have then TDS also to the extent of about Rs. 50K. After crossing the income limit of Rs. 10L, you will get into 30% slab. Here your TDS @ 10% will be short of your tax liability on income above Rs. 10L @ 30%. You will then have to pay advance Tax. This is only rough estimate.The exact workings depend upon your actual income, expenses and deductions.
3) You need to maintain accounts like cash book, bank statements and bills for your professional income to justify your incomes and expenses.
4) If your professional income exceeds Rs 25 L, then your accounts will have to be audited by a CA.