HTK (electronic building ID)
The electronic building ID: a digital record of a building's key data, permits and energy class. It may be needed for permits, property transfers and other procedures.
The Electronic Building ID (HTK) records a building's key data, including its floor area, permits and energy performance. It is issued electronically, usually with an engineer's help.
For small works, the HTK can affect whether a permit is needed and what the process costs. Check with your engineer or the local building office which details apply to your building.
Official source: Ministry of Environment and Energy