(a)the amount of duty chargeable on such instrument [or a copy of the instrument] [Inserted by Maharashtra 17 of 1993, Section 32(b) (w.e.f. 1.5.1993).] shall be the amount of duty chargeable under Schedule I on a document of the like description executed in this State less the amount of duty, if any, already paid under any law in force in India excluding the State of Jammu and Kashmir on such instrument when it was executed;
