(1)This section applies to determine when expenditure is treated as incurred for the purposes of sections 139 and 140.
(2)The general rule is that an amount of expenditure is treated as incurred as soon as there is an unconditional obligation to pay it.
(3)The general rule applies even if the whole or a part of the expenditure is not required to be paid until a later date.
(4)There are the following exceptions to the general rule.
(5)If under an agreement—
(a)the expenditure is on the provision of an original master version,
(b)an unconditional obligation to pay an amount of the expenditure comes into being as a result of the giving of a certificate or any other event,
(c)the giving of the certificate, or other event, occurs within the period of one month after the end of a relevant period, and
(d)at or before the end of the relevant period, the original master version has become the property of, or is otherwise under the agreement attributed to, the person subject to the unconditional obligation to pay,
the expenditure is treated as incurred immediately before the end of the relevant period.
(6)If under an agreement an amount of expenditure is not required to be paid until a date more than 4 months after the unconditional obligation to pay has come into being, the amount is treated as incurred on that date.
(7)If under an agreement—
(a)there is an unconditional obligation to pay an amount of expenditure on a date earlier than accords with normal commercial usage, and
(b)the sole or main benefit which might (as a result) have been expected to be obtained is that the amount would be treated, under the general rule, as incurred at an earlier time,
the amount is treated as incurred on the date on or before which it is required to be paid.