Section 23 of the Principal Act is hereby amended -
(a) in subsection (1):
(i) by the substitution of "assessment" for "estimate", and
(ii) by the substitution of "assessed" for "estimated",
and
(b) by the insertion of the following subsection after subsection (2):
"(3) Where a person appeals an assessment under subsection (1), within the time limits provided for in subsection (2), he shall pay to the Revenue Commissioners the amount which he believes to be due, and if -
(a) the amount paid is greater than 80 per cent. of the amount of the tax found to be due on the determination of the appeal, and
(b) the balance of the amount found to be due on the determination of the appeal is paid within one month of the date of such determination,
interest in accordance with section 21 shall not be chargeable from the date of raising of the assessment.".