[tuatoru]

I don't think it would be hard to apply a CGT to real estate only, as all transactions are centrally recorded, but it would disincentivise exchange (which presumably occurs when the buyer sees a more valuable use for the land), unless it is charged on unrealised gains, which is a can of worms.

Other possible measures:-

Stamp duty, as in the UK. Also disincentivises exchange.

Unimproved land value tax (Georgism). (Would need to apply to alienable land only, or there would be significant impact on rural iwi, and possibly a threshold of say $100k/ha unimproved land value since farmers whinge so loudly.) Fewest problems in tax policy terms.

Revise zoning. Change residential to mixed use (light traffic commercial, up to 25 employees, say), allow up to four storey and multiple-household buildings, prohibit "amenity" and "character" objections to consents (apart from noise and smell) and building size/usage/land use covenants near (<10 km radius) the centres of cities, and probably some other measures. Densification policies. Streamlined planning and consenting of developments.

I agree that we need to build capital for business investment. Tax policy (and middle class culture, as embodied in zoning rules and district plans) is heavily tilted against that. Been that way my whole life.