In brief, a holding means an asset that is any land, with or without buildings thereon. Referring to the definition of "annual value" in Section 2 (Interpretation) under Local Government Act 1976 (Act 171):
"Annual value" means the estimated gross annual rent at which the holding might reasonably be expected to let from year to year the landlord paying the expenses of repair, insurance, maintenance or upkeep and all public rates and taxes:

Under this interpretation, there is a condition stating that any vacant land is also charged with assessment tax that is under part (c) ii

Provided that—
(a) in estimating the annual value no account shall be taken of any restrictions or control on rent in so far as it limits the rent which may be required by a landlord or recovered from a tenant of a holding;
(b) in estimating the annual value of any holding in or upon which there is any machinery used for any or all of the following purposes:
i.  the making of any article or part of an article;
ii. the altering, repairing, ornamenting or finishing of any article;
iii.the adapting for sale of any article,
(c) in the case of any land—
i. which is partially occupied or partially built upon;
ii. which is vacant, unoccupied or not built upon;
iii.with a building which has been certified by the local authority to be abandoned or dilapidated or unfit for human habitation.

The annual value shall be, in the case of subparagraph (i), either the annual value as hereinbefore defined or ten per centum of the open market value thereof at the absolute discretion of the Valuation Officer, and in the case of subparagraphs (ii), (iii) and (iv) the annual value shall be ten per centum of the open market value thereof as if, in relation to subparagraphs (iii) and (iv), it were vacant land with no buildings thereon and in all cases the local authority may, with the approval of the State Authority, reduce such percentages to a minimum of five per centum;

(d) where in respect of any particular holding, in the opinion of the Valuation Officer, there is insufficient evidence to base a valuation of annual value upon, the Valuation Officer may apply such methods of valuation as in his opinion appears appropriate to arrive at the annual value.