The point of the system where you have to accept an offer at your supposed valuation is that it forces accurate valuations.
If you now say that we need to provide two different valuations (land + structure) but we're only taxed on one, don't you think we'll find that everyone lives in very expensive houses on worthless plots of land?
No, because it's much easier to independently value a house
What are you suggesting as an alternative?
- Both taxation and offer on the improved value - this is consistent, but it's no longer Georgism so it doesn't solve the problem of how to estimate and tax the unimproved value
- Both taxation and offer on the unimproved value - this is now unfair to the owner as you're not paying for the value of their house, and also they have the incentive to include the value of the house in the land value
If you now say that we need to provide two different valuations (land + structure) but we're only taxed on one, don't you think we'll find that everyone lives in very expensive houses on worthless plots of land?