Having one legal title at the present moment should not make it impossible to sell off one of the units. There are countless buildings in Dublin, many dating from the nineteeth century that were formerly large posh houses, that previously had one legal title and over the years have been divided into apartments (or offices).
These buildings often have gardens, and they all have "shared" halls, corridors and stairwells. The deeds of each apartment usually refer to common useage of such shared facilities and the liability of the owners for the upkeep of gardens, roofs, halls, corridors,stairs etc.
I own a building in the heart of Dublin that is divided into a few apartments and a shop. It has,at present, one legal title. Does that mean I should submit one value for the whole building ,rather than for each seperate apartment?
I still suspect that the authorities expect each self-contained unit to be regarded as a seperate property for the purpose of this wretched tax.