Unfortunately, there are agents who tell homeowners that a home will not sell for more than the Assessed Value which the town assessor has placed on the home. This is just not true.
The assessed value is a value given by the local Assessor for tax purposes only. They do not gain access to the interior of the home which can increase or decrease the assessed value if the appraiser had viewed the home. It is based on square footage,upgrades that the town has knowledge of(fireplaces,central air and decks-the town can see these upgrades from the outside or use permits to add value).
I have had homes that were assessed for tens of thousands less than what I sold the home for. I have also had homes that sold for less than assessment due to condition. I had a home that was assessed for $138,000 which sold for $190,000. Buyers ask me why they would pay so much more than assessment for a home. I advise then that for the same reason they would not pay over asking just because the town has it assessed higher.
Your home's value is a case-by-case basis and only effects your home's value when a buyer or agen uses it to justify a price. Only a complete market value analysis by an experienced professional can give you a true value. Even then, some buyers will pay top dollar while others are negotiators to try to get the best price. Your listing agent should protect you from aggressive buyers and agents and help justify the value as your agent.