Your problem will come if you disagree with the final assessment at which time you will have to provide some evidence of the property's value, like an appraisal. The city/town gets to make their appraisal and the appeals board is not going to yours much weight if you don't allow access. The Assessor/appraiser is not interested in making life hard on you. With, for all practical purposes, no sales or personal income tax, communities are heavily dependent on the property tax. Most try hard to levy that tax as fairly as possible. If you don't like the system, work to change it or maybe live somewhere else.