In most cases, upon disposal of a foreign property you will have paid CGT in the foreign jurisdiction. Therefore, depending on whether a double tax agreement exists between Ireland and the relevant country, you should be entitled to a tax credit in Ireland for any foreign tax paid on the gain.
A notable exception – France: There is currently no article on CGT included in the Ireland/France double tax agreement. This could therefore result in the disposal of a French property being taxed twice i.e. in France at a rate of 16% and in Ireland at a rate of 20%.
Note: As the Ireland/France treaty is expected to be revised it may be possible to apply to Revenue for relief from this potential double hit on a concessionary basis. Detailed advice should be sought prior to sale.