Some profits or losses arising under a lease may not be
accounted for through rental earnings or as interest. ICTA88/S502C
applies to a profit or loss (whether capital or revenue in nature)
that
Where this is the case any profit is treated as income
attributable to the lease. Therefore if the rental earnings would
be taxed as trading income, so is the exceptional profit. But if,
for example, the rental earnings would be taxed as property income
(as may be the case with fixtures) the exceptional profit would
also fall to be taxed property income.
Note that it does not matter whether the profit has been
realised in the sense that money etc may have been received: what
matters is that is has been recognised for accounting purposes.
Similar principles apply to a loss, which is treated as if it
were revenue expenditure incurred in connection with the lease.
See example at
BLM40125.