Any cash payment or aggregate of cash payments during a day exceeds Rs 20,000/- will attract dis allowance of the expenditure u/s 40A (3) and (3A) of the Income Tax Act. Accordingly, the purchases made by you in cash will be disallowed and added to your business income.
As you are doing business, you need to have PAN, as you will not be able to make transactions above Rs 50K through your bank account. Secondly if there is taxable income, you need to file your IT return. Finally if there is no business loss, you can carry forward your loss for set off against your future income, provided you file your IT return within the due date.Further, wherever TDS is attracted, Tax will be deducted at maximum rate or 20%, whichever is higher and you may not be able to claim credit for TDS, It is therefore advisable for you to have PAN.