Currently if your only income is from PAYE wages/salary you aren't required to file a return. Wouldn't a simple land tax billed with the rates notices be easier to administer, more efficient to collect, and not require a whole lot more people to file tax returns? The land tax rate could be based on the regional or national average amount of time the value of the land doubles. I understand your proposal is a tax on a deemed rate of return rather than a tax on capital gains. Does your proposed deemed rate factor in the usual capital gain as well as the annual "market rate" rental? If not, I'm afraid there is still an incentive to gear up on property.
Not really - its very easy to get your house value from the local council, your insured value from an insurance company, and your mortgage from a bank. The IRD has many rights. You don’t need to do anything if it’s just the home that’s involved. If there are other assets you might need to fill an online form, sign a statutory declaration. Very simple really, no accountants needed that’s for sure.