The scenario wherein shares are bought but not received by you within the set time limit T+1 working days(trade day + 1 working day) is known as short allotment. However, you would most probably receive the shares in your demat account within T+2 working days(trade day+2 working days).

In case of market shortage, the shares are allotted to the client in T+2 working days. If the purchase from the market is not possible, the client will receive a credit amount in his trading account for that particular share according to exchange rules.