SqFt Wrong on Tax Record

[Daniel Sharp]

Quick 2-part question, here’s the situation:

Owner has a house built in 1986.  Has an addition done to the house in 1997, which increases the SqFt of the property.  The owner is told by the contractor that he will take care of letting the tax office know about the new SqFt of the home, but never does and the owner doesn’t follow up.  Now the owner is looking to sell the home, gets a realtor to list the home, and realizes his SqFt in his taxes has been wrong the past 25 years.

Question 1: How do we go about fixing the tax record?

Question 2: Will there be a penalty for paying taxes on a “smaller” house the past 25 years?  If yes, is there a way to avoid this penalty?

Thanks!