27(1)If, in respect of an accounting period, an officer of Revenue and Customs discovers that—U.K.
(a)an amount of multinational top-up tax that ought to have been assessed in respect of a multinational group has not been assessed, or
(b)an assessment to tax is or has become insufficient,
the officer may make an assessment (a “discovery assessment”) in the amount which ought in the officer's opinion to be charged in order to make good to the Crown the loss of tax.
(2)This is subject to the restrictions in paragraph 28.