A person on whom a completion noticed is served may, during the period of twenty-one days beginning with the date of service of the notice, appeal to the valuation appeal committee against the notice on the ground that the erection of the building to which the notice relates has not been, or, as the case may be, cannot reasonably be expected to be, completed by the date specified by the notice.

If a completion notice served in respect of a building is not withdrawn and no appeal is brought under this paragraph against the notice or such an appeal is abandoned or dismissed, the erection of the building shall be treated for the purposes of this Schedule as completed on the date specified by the notice; and if such an appeal is brought and is not abandoned or dismissed and the completion notice in question is not withdrawn, the erection of the building shall be treated for those purposes as completed on such date as the valuation appeal committee shall determine.