File vat return without any bills

i have a small kirana store, Turnover Approximately 14 Lakhs p.a. i am purchased kirana items from local guys without any vouchers/Receipts and i sale MRP Price to retail. i have no vouchers/bills/Receipts on both sales & Purchases. but i have TIN. now how to file vat returns without any bills. In our small town, other small kirana shops file their vat returns without any bills through Local Tax consultants. how its possible without any bills