http://www.legislation.gov.uk/id/anaw/2017/1/schedule/6/part/5

SCHEDULE 6LEASES

The NPV of the rent payable over the term of a lease is calculated by applying the following formula—

NPV = \sum_{i = 1}^{n} \frac{r_{i}}{{(1 + T)}^{i}}

Figure 8 where—

r_i is the rent payable in respect of year i,

i is the first, second, third etc. year of the term of the lease,

n is the term of the lease, and

T is the temporal discount rate (see paragraph 32).