9(1)Subject to sub-paragraph (2) below, where the Commissioners make an assessment under paragraph 12 below of an amount of interest payable at the rate given by paragraph 8(3)(a) above, that amount shall carry penalty interest for the period which—
(a)begins with the day on which the assessment is notified to the person on whom the assessment is made; and
(b)ends with the day before the day on which the assessed interest is paid.
(2)Where—
(a)the Commissioners make an assessment under paragraph 12 below of an amount of interest due from any person,
(b)they also specify a date for the purposes of this sub-paragraph, and
(c)the amount of interest assessed is paid on or before that date,
the amount paid before that date shall not carry penalty interest under this paragraph.