It may be that the lease has provided for the rental to be set according to some variables – for example, rent is based on the annual turnover of the tenant, or adjustable to open-market rent on review.
Where rent is variable, a reasonable estimate of the rent for each year of the lease should be used for the purpose of determining LBTT liability (Sch. 19, para. 13(1), (2)).
In the case of an open-market rent review, it is normally acceptable to estimate the rent payable after review as being the same as the passing rent (See RS Guidance LBTT6005).