56(1)If a person is liable to a penalty under this Part of this Schedule, HMRC must—
(a)assess the penalty, and
(b)notify the person.
(2)The assessment of a penalty—
(a)is to be treated for procedural purposes in the same way as an assessment to tax (except in respect of a matter expressly provided for by this Schedule),
(b)may be enforced as if it were an assessment to tax, and
(c)may be combined with an assessment to tax.
(3)A supplementary assessment may be made in respect of a penalty if an earlier assessment is based on an amount of tax due and payable that is found by HMRC to be an underestimate or insufficient.
(4)Sub-paragraph (5) applies if—
(a)an assessment in respect of a penalty is based on a liability to tax that would have been shown in a return, and
(b)that liability is found by HMRC to be excessive.
(5)HMRC may by notice amend the assessment so it is based on the correct amount.
(6)An amendment under sub-paragraph (5)—
(a)does not affect when the penalty must be paid;
(b)may be made after the last day on which the assessment in question could have been made (under sub-paragraph (7)).
(7)An assessment of a penalty must be made before the end of the period of 12 months beginning with—
(a)the end of the appeal period for the assessment of the liability to tax which would have been shown in the return, or
(b)if there is no such assessment, the date on which that liability is ascertained or it is ascertained that the liability is nil.
(8)In sub-paragraph (7) “appeal period” means the period during which—
(a)an appeal could be brought, or
(b)an appeal that has been brought has not been determined or withdrawn.
(9)A penalty must be paid before the end of the period of 30 days beginning with the day on which notification of the penalty is issued.