Looks like my gut was right.
Tax payable date is 1st January, except salary deduction cases.
Interest accrues from the payment date, so from 1st January in all cases except salary deduction cases.
In cases where one of the phased or deferred payment options (DD, SDA) are chosen, then interest will not be charged - so clearly without that provision interest would be due on those payment options.
http://www.irishstatutebook.ie/2012/en/act/pub/0052/sec0119.html#sec119
"(1) Subject to
subsection (2), local property tax contained in a self-assessment or a Revenue assessment or treated as contained in a Revenue assessment under
section 49 shall be
payable on or before—
(
a) 1 July 2013, in respect of the liability date 1 May 2013, and
(
b)
1 January, in respect of the liability date 1 November in any other year.
(2) Local property tax which is deductible by an employer under
section 74 shall be payable within the period specified in Regulation 28(1) and (1A) or Regulation 29(1) and (1A), as the case may be, of the PAYE Regulations (within the meaning of
section 64 ).
(3) Local property tax which is deductible—
(
a) by the Minister for Social Protection under
Chapter 2 of
Part 10 , and
(
b) by the Minister for Agriculture, Food and the Marine under
Chapter 3 of that Part,
shall be payable within the period specified in
section 93 (3) and
section 111 (3), respectively."
http://www.irishstatutebook.ie/2012/en/act/pub/0052/sec0149.html#sec149
"(1) Subject to
subsection (4), any local property tax payable by—
(
a) a liable person, or
(
b) a person who is directed by the Revenue Commissioners to deduct local property tax under
Chapter 1 ,
2 or
3 , as the case may be, of
Part 10 ,
shall carry interest from—
(i) the date on which the tax is payable, or
(ii) the last day of the period within which the tax is payable,
until payment and the amount of that interest shall be determined in accordance with
subsection (2).
(2) The interest referred to in
subsection (1) shall be determined by using the following formula:
T x D x R
where—
T is the local property tax payable which remains unpaid,
D is the number of days (including part of a day) in the period during which the local property tax remains unpaid, and
R is the rate of 0.0219 per cent."
(3) The interest payable under this section—
(
a) shall not be allowed as a deduction in computing any income, profits or losses for any of the purposes of the Tax Acts,
(
b) may be collected and recovered in like manner as an amount of local property tax,
(
c) shall be payable to the Collector-General, and
(
d) shall be deemed to be a debt due to the Minister for the benefit of the Central Fund.
(4)
Where a liable person—
(a) elects for a method of payment in a return, and
(b) pays the amount of local property tax in the self-assessment in the return in accordance with that method,
interest shall not be charged"