We hear this one on the phone: "I filed last year. Then my assessment went up. Did I do that to myself?" Other people ask before they file. They worry the county will take a second look at the house and find a reason to charge more.
The county's own answer is no. The board that hears appeals, the Assessment Review Commission (ARC), can lower the number you appealed or leave it as it is. Those are its two choices. It can't raise the assessment because you filed.
Two years can overlap
Each January the county posts a new value for your home. That's the tentative assessment. ARC can take up to 15 months to decide a case. So next January's number can land in your mailbox before you hear about last year's appeal.
A different office sets that new number. The Department of Assessment values the whole county each year, whether or not you appealed. A higher number on the new notice belongs to the new year. Your appeal covers last year's number, and ARC decides that one on its own.
Other reasons a number can go up
An addition or a renovation can raise the value the county puts on your home. The county limits how much a home's assessment can rise in one year to 6 percent. That limit doesn't cover value added by construction or renovation.
A late win can cause a surprise. Say ARC lowered your number, but the decision came after the county had set next January's value. The county says your reduced number is the base for the next year's 6 percent limit. If the new number rose more than 6 percent for this reason, you have the right to a correction. To keep that right, appeal the new number and contact the Department of Assessment.
The county has one more way to change a number. If it finds a clerical error or a mistake in the basic facts about a home, the Department of Assessment can ask ARC to fix it before that year's roll becomes final. The fix can go up or down. It's a separate process from your appeal.
File for each year
The county treats each year as its own case. If you disagree with the new January number, file on that number, even while last year's case is open. Waiting for the older decision can cost you this year's filing window. Our Nassau grievance calendar shows when the new number posts and when filing closes.
Filing doesn't freeze next year's number. The county posts a new value each January, filed or not.
Check it yourself
Each rule in this post is on ARC's own FAQ page, in the county's words.