The seller of goods is deemed to be an "unpaid seller" within the meaning of this Act—

(a) when the whole of the price has not been paid or tendered;

(b) when a bill of exchange or other negotiable instrument has been received as conditional payment, and the condition on which it was received has not been fulfilled by reason of the dishonour of the instrument or otherwise. [S. 45(1) of the Sale of Goods Act, 1930]

So far as the right of unpaid seller is concerned it is the quantum of damages for non-acceptance of goods property in which already passed to buyer- Measure of damages is the difference between the contract price and the market price as prevailed on the date when non-acceptance took place. [Messers. Arag Ltd. vs. Muhammad Ismail (1968) 20 DLR (WP) 242]