Talk to the assessor before you file
The cheapest correction is the one that never becomes an appeal.
The township assessor produced the number. They can often change it without a hearing, and they are usually willing to when the record is plainly wrong.
What this fixes
Factual errors: square footage, a bathroom that does not exist, a basement recorded as finished, a demolished outbuilding, a garage counted twice, the wrong class after a conversion.
How to do it
Call or email. Give the PIN. State the specific fact that is wrong and what it should be, and offer evidence — photographs, a survey, plans, a contractor's letter. Ask for the property record card, which is what the county holds about your house; reading it is often where the error becomes obvious.
Why it is better than filing
Faster, no deadline pressure, and it does not open your whole assessment to a board that can raise it.
When to stop and file
If the disagreement is about value or uniformity rather than fact, the assessor is unlikely to move, and the board is the right forum. Do not let a friendly conversation run past the filing deadline — note the date, and file if it approaches without resolution.