Section 26

A lease or an agreement for a lease or with respect to any letting is not chargeable 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.

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 the lessee having previously made, any substantial improvement of or addition to the property demised to the lessee, or of any covenant relating to the matter of the lease, is not chargeable with any duty in respect of such further consideration, except where such further consideration consists of a covenant which if it were contained in a separate deed would be chargeable with ad valorem duty.

An instrument by which the rent reserved by any other instrument chargeable with duty and duly stamped as a lease is increased is not chargeable with duty otherwise than as a lease in consideration of the additional rent thereby made payable.