When did the improvement become usable or substantially complete?
Why you received one
The tax list can change after the regular October assessment date.
The New Jersey Division of Taxation explains that owners sometimes make changes or additions to real property after October 1, when values are set for the following tax year. If that work creates added value, an additional assessment can be sent to the owner.
An omitted assessment is related but different. It is used when taxable property was left off the municipality's tax list in error.
Important: an added assessment is about added taxable value, not simply what you spent on the project. Cost and assessed value are different concepts.
01 · Check the notice
Match the added value to the property and the work.
Before deciding whether the number is reasonable, confirm the underlying facts.
Confirm municipality, block, lot and qualifier.
Identify the improvement or change the assessor is recognizing.
Separate the original assessment from the added assessment amount.
Check the effective period shown on the notice and the additional tax amount.
If the property description is wrong, document the error before discussing value.
02 · The right question
Ask what value the completed work added, not what the contractor charged.
A $100,000 renovation does not automatically create $100,000 of taxable value, and a lower-cost project can still change value materially.
Did square footage, use, bedroom count, finished area or other recorded characteristics change?
How does the improved property compare with similar completed properties in the same market?
Make sure you are not treating the added value as though it replaced the full original assessment.
03 · If you disagree
Added assessments have their own appeal path.
The state directs added or omitted assessment appeals to the County Board of Taxation using Form AA-1. Use the deadline and instructions on the current notice and county materials because timing can differ from the ordinary annual appeal process.
Official source