4. In section 9 (Class 4 contributions recoverable under Tax Acts)—
(a)in subsection (1), after “payable”, where first occurring, insert “for any tax year”;
(b)in that subsection, for the words from “any year” to “1975” substitute “the year of assessment corresponding to that tax year”; and
(c)after that subsection insert the following paragraph—
“For the purposes of this section the year of assessment which corresponds to a tax year is the year of assessment (within the meaning of the Tax Acts) which consists of the same period as that tax year.”.