19(1)Where a person is liable for a penalty under paragraph 1 HMRC must—U.K.
(a)assess the penalty, and
(b)notify the person.
(2)If—
(a)HMRC do not have all the information required to determine the amount or value of the relevant consideration within the meaning of paragraph 15, and
(b)HMRC have taken all reasonable steps to obtain that information,
HMRC may assess the penalty on the basis of a reasonable estimate by HMRC of that consideration.
(3)This paragraph is subject to—
(a)paragraphs 21 and 22 (limits on when penalty may be assessed); and
(b)Part 7 of this Schedule (requirement for opinion of GAAR Advisory Panel before penalty may be assessed).