(1) A lease, or agreement for a lease, or with respect to any letting, shall not be charged with any duty in respect of any penal rent, or increased rent in the nature of a penal rent, thereby reserved or agreed to be reserved or made payable, or by reason of being made in consideration of the surrender or abandonment of any existing lease, or agreement, of or relating to the same subject matter.

(2) A lease made for any consideration in respect of which it is chargeable with ad valorem duty, and in further consideration either of a covenant by the lessee to make, or of such lessee having previously made, any substantial improvement of or addition to the property demised to such lessee, or of any covenant relating to the matter of the lease, shall not be charged with any duty in respect of such further consideration.

(3) Subsection (2) shall not apply as respects any further consideration in the lease consisting of a covenant which if it were contained in a separate deed would be chargeable with ad valorem stamp duty and, accordingly, the lease shall in any such case be charged with duty in respect of any such further consideration under section 7.

(4) An instrument whereby the rent reserved by any other instrument chargeable with duty and duly stamped as a lease is increased shall not be charged with duty otherwise than as a lease in consideration of the additional rent thereby made payable.

(5) Where -