Indian Stamp Act, 1899
4. Several instruments used in single transaction of sale, mortgage or settlement
(1) Where, in the case of any sale, mortgage or settlement, several instruments are employed for completing the transaction, the principal instrument only shall be chargeable with the duty prescribed in Schedule I, for the conveyance, mortgage or settlement, and each of the other instruments shall be chargeable with a duty of one rupee instead of the duty (if any) prescribed for it in that Schedule.
(2) The parties may determine for themselves which of the instruments so employed shall, for the purposes of sub-section (1), be deemed to be the principal instrument:
PROVIDED that the duty chargeable on the instrument so determined shall be the highest duty which would be chargeable in respect of any of the said instruments employed.