Also called PO, supplier order
A purchase order, or PO, is your written order to a supplier. It lists what you want, how much, at what price and by when. Once the supplier accepts it, it is the agreed basis for the delivery and the bill.
Ordering by phone works until something arrives that you did not ask for, or at a higher rate. A PO gives you something to check the delivery and the bill against. It also tells you what is already on the way, so you do not order the same thing twice.
A shop raises a PO for 30 cases of tea at ₹2,400 a case, ₹72,000 before GST. The supplier sends 25 now and promises 5 next week. The PO stays open for the remaining 5 until they arrive or are cancelled. Kownt X can raise POs straight from the reorder list.