Yes, you may refuse entry to your home, but is in your best interest to see that as much information as possible is gathered to help insure an accurate assessment. If an appraiser cannot inspect the inside of a building, it's possible an inaccurate assessment may result. The law provides that a property can be assessed at the highest reasonable value if the field inspector is denied entry.
The revaluation program should not be seen as an adversarial situation. Property owners have a vested interest in the outcome of the project and their cooperation is vital to achieve an equitable revaluation. If one person's property is under-assessed, all the other property owners in the municipality will pay higher taxes to make up for the discrepancy. Conversely, if property owners deny access to the field inspector they could wind up being over-assessed and pay more than their fair share of taxes.