Mercer Property Tax: Rates, Deadlines & Tax Board Appeals

For a standard 2026 Mercer County residential assessment appeal, the filing deadline was Wednesday, April 1, 2026; the Mercer County Board of Taxation says filings are accepted 8:30 a.m.–4:00 p.m. and must be received, not just postmarked. File with the Mercer County Board of Taxation, 640 South Broad Street, Room 317, Trenton, NJ 08611, and serve copies on your municipal assessor and municipal clerk; fax and email copies are not accepted.

As of October 6, 2026, the next regular assessment-appeal deadline is expected to be April 1, 2027 under the statewide rule, unless your municipality has a later 45-day notice date or a revaluation/reassessment year rule applies. Added/omitted assessment appeals use a separate December 1 deadline.

How assessments work in Mercer County

Mercer County’s appeal body is the Mercer County Board of Taxation, not your mortgage company and not the county tax collector. The Board certifies assessments and tax rates, supervises municipal assessors, produces the abstract of ratables and equalization table, and hears real-property assessment appeals.

Your assessment is set locally by your municipal tax assessor—East Windsor, Ewing, Hamilton, Hightstown, Hopewell Borough, Hopewell Township, Lawrence, Pennington, Trenton, Robbinsville, West Windsor, or Princeton. Mercer says assessment notice postcards are mailed at the end of January every year; review that card before deciding whether to appeal.

For appeals, the key valuation date is October 1 of the pretax year. For a 2026 appeal, you had to prove the property’s market value as of October 1, 2025. New Jersey’s 2026 revaluation/reassessment approval list does not list any Mercer municipality, so the ordinary 2026 Mercer deadline remained April 1 and the Board used the Chapter 123 common-level test rather than a new 100% revaluation standard.

The state’s 2026 Chapter 123 ratios matter because your assessment is not automatically reduced just because your house could sell for less than the assessed number. You generally need to show your assessment-to-market-value ratio is above the municipality’s upper limit. Examples for tax year 2026: Hamilton’s average ratio was 61.32% with a 70.52% upper limit; Princeton’s average ratio was 62.64% with a 72.04% upper limit; Trenton’s average ratio was 53.53% with a 61.56% upper limit.

Whether you should appeal

Appeal the assessment, not the tax bill. A higher tax bill caused by school, municipal, county, library, or open-space budgets is not enough. Your best case is usually one of these:

• Your assessment implies a market value higher than comparable sales support.
• Your property record card has an error: wrong living area, finished basement, number of baths, garage, condition, or lot assumptions.
• You bought the home in an arm’s-length sale before October 1, 2025 and the assessed value is inconsistent with that sale after applying the Chapter 123 ratio.
• Similar, nearby sales before October 1, 2025 support a lower true market value.

Use Mercer’s County Information Portal / assessment records to pull your property record card, sales history, deed and comparable sales. The official Comparable Sales Analysis form asks for three comparable sales, but the brochure says 3 to 5 sales are useful. Listings, Zillow estimates, neighbor assessments, and “my taxes are too high” arguments are weak. Sales are strongest when they are close in location, age, style, lot size, condition, gross living area, bedroom/bath count and sale date.

Mercer County does not appear to publish an official appeal success rate or median reduction table on its Board of Taxation pages. Do not assume a reduction; the Board can also increase an assessment if your evidence shows it is below the common-level range.

Step-by-step how to file

1. Confirm your assessment and municipality. Use your January assessment postcard and the Mercer property records site. Check block, lot, qualifier, land assessment, improvement assessment and total assessment.

2. Talk to the municipal assessor first. Mercer’s brochure strongly recommends checking facts and discussing the assessment with the assessor before filing. This does not extend the deadline.

3. Choose the correct form. For a normal assessment appeal, use Form A-1, Petition of Appeal – County Board of Taxation. For sales evidence, use Form A-1 Comp. Sale / Comparable Sales Analysis Form. For an added or omitted assessment, use Form AA-1, Added/Omitted Assessment Appeal.

4. Prepare copies and service. If you download the petition, Mercer says one copy must be served on the Mercer County Board of Taxation, one copy on the municipal assessor, and one copy on the municipal clerk. The County Board address is 640 South Broad Street, Room 317, Trenton, NJ 08611. Use your municipality’s official assessor and clerk addresses for the other two copies.

5. Do not email or fax the filing. Mercer’s appeal-instructions page states that fax and email copies will not be accepted. In-person filings are accepted 8:30 a.m.–4:00 p.m. The county page also makes forms available at the Tax Board office, municipal assessor’s office, or by telephone request. If you mail, build in delivery time because the petition must be received by the deadline.

6. Include the filing fee. Mercer lists these fees: assessed value under $150,000: $5; $150,000 to under $500,000: $25; $500,000 to under $1,000,000: $100; $1,000,000 or more: $150. Classification appeals are $25; valuation plus classification is the sum of both fees.

7. Keep taxes current. Mercer says all real-estate taxes and municipal charges through the February 1 payment must be current for the case to be heard.

What happens after

Mercer schedules a hearing before the County Tax Board. The Board consists of three governor-appointed members, and hearings are public meetings presided over by one or more tax commissioners. The municipality is the opposing party and may be represented by the municipal attorney; the assessor or an appraiser may appear as an expert.

Hearings are generally held after the April 1 deadline, during the work week starting at 9 a.m. Adjournments are generally denied. If you do not appear and do not have a postponement, the case can be dismissed for lack of prosecution, and Mercer warns that such judgments are final for that year and cannot be further appealed to Tax Court.

A hearing is technically always necessary, but you may not need to attend if the taxpayer, assessor and municipal attorney settle and submit a signed settlement stipulation to the Board for approval before the hearing. If you rely on an appraisal, the appraiser must be available to testify and be cross-examined; Mercer says appraisal reports must be supplied in advance.

Evidence must be submitted to the assessor and Tax Board at least seven days before the hearing. Mercer’s Comparable Sales Analysis form says to submit five copies to the Tax Board and one copy each to the assessor and municipal clerk no later than seven days prior.

Mercer says the Board usually renders a decision 6 to 8 weeks after the hearing. If you disagree, you have 45 days from the mailing date of the judgment to appeal to the Tax Court of New Jersey. Properties assessed over $1,000,000 may file directly with Tax Court by April 1 instead of starting at the County Board.

Local tips

Use the tax rate for your municipality, because Mercer has no single residential rate. The county’s latest posted breakdown lists 2025 total rates including: Princeton 2.733, Hopewell Township 3.129, West Windsor 3.162, Hamilton 3.708, Ewing 4.051, Hightstown 5.109, and Trenton 5.890 per $100 of assessed value.

Worked example: assume a Hamilton homeowner has a $420,000 assessment. Strong comparable sales support a $550,000 true market value. Hamilton’s 2026 Chapter 123 upper limit is 70.52%, so the assessment-to-value ratio is $420,000 ÷ $550,000 = 76.36%, above the upper limit. If the Board agrees, the adjusted assessment would generally be market value × average ratio: $550,000 × 61.32% = $337,260. Reduction: $82,740. Using Hamilton’s 2025 total rate of 3.708 per $100, estimated annual savings are $82,740 ÷ 100 × 3.708 = about $3,068. That is only an estimate; the final tax effect depends on the certified rate for the tax year and any judgment wording.

Finally, check relief programs separately from assessment appeals. New Jersey’s combined property-tax-relief application covers ANCHOR, Senior Freeze and Stay NJ, with a 2025 application deadline of November 2, 2026. Also ask your municipal assessor about the $250 senior/disabled deduction, $250 veterans deduction, and the full exemption for qualifying 100% permanently and totally disabled veterans. These programs reduce tax liability but do not prove your assessment is wrong.

Mercer County Property Tax Rate

No single countywide homeowner tax rate was found; Mercer County rates are certified by municipality/taxing district. Latest official NJ Treasury Mercer Abstract available: 2025 Total General Tax Rates, expressed as dollars per $100 of taxable assessed value (multiply by 10 for mills): East Windsor Twp. 3.627; Ewing Twp. 4.051; Hamilton Twp. 3.708; Hightstown Boro. 5.109; Hopewell Boro. 3.498; Hopewell Twp. 3.129; Lawrence Twp. 3.165; Pennington Boro. 3.308; Trenton City 5.890; Robbinsville Twp. 3.488; West Windsor Twp. 3.162; Princeton 2.733.

Source: https://www.nj.gov/treasury/taxation/pdf/lpt/ratables/Mercer2025.pdf

When Are Property Taxes Due in Mercer County?

For New Jersey calendar-year municipalities, property taxes are payable in four installments due February 1, May 1, August 1, and November 1; unpaid amounts become delinquent after those dates, subject to any local statutory grace period. Four quarterly installments: 1st on February 1, 2nd on May 1, 3rd on August 1, and 4th on November 1.

This is not the same as the assessment appeal deadline above. The appeal deadline is your window to contest your assessed value; the payment due date is when the resulting tax bill must be paid. Missing one does not affect the other, but missing either has real consequences — one forfeits your right to appeal for the year, the other can trigger penalties and interest.

Source: https://www.nj.gov/dca/dlgs/programs/tax_collector_docs/guidetocalcesttaxes.pdf

Property Tax Exemptions in Mercer County

• $250 Senior Citizens and Disabled Persons Property Tax Deduction — Homeowners age 65 or older, or disabled, who have been New Jersey residents for at least one year, own and occupy the home as of October 1 of the pretax year, file a timely application, and meet the income threshold; qualifying surviving spouses/civil union partners may also qualify.. Annual $250 property tax deduction. Yes; file Form PTD and documentary proofs with the local assessor or tax collector. To maintain the deduction, file Form PD5 with the tax collector annually. Apply by PD5 continuation form due on or before March 1 each year; initial application deadline not stated on the source.. (Source: https://www.nj.gov/treasury/taxation/lpt/lpt-seniordeduction.shtml)
• $250 Veterans Property Tax Deduction — Honorably discharged veterans with active-duty U.S. Armed Forces service who are New Jersey legal residents and own the property as of October 1 of the pretax year; qualifying surviving spouses/civil union/domestic partners may also qualify.. Annual $250 property tax deduction. Yes; file Form V.S.S. and documentary proofs with the local assessor or tax collector. Apply by Eligibility requirements must be met as of October 1 of the pretax year; no separate filing deadline was stated on the source.. (Source: https://www.nj.gov/treasury/taxation/lpt/lpt-veterans.shtml)
• 100% Disabled Veteran Property Tax Exemption — Honorably discharged veterans who were 100% permanently and totally disabled during active-duty service, are New Jersey legal residents, own and occupy the dwelling as their main home, and provide VA certification; qualifying surviving spouses/civil union/domestic partners may also qualify.. Annual property tax exemption on the principal or primary residence. Yes; file Form D.V.S.S.E. and documentary proofs with the local assessor. (Source: https://www.nj.gov/treasury/taxation/lpt/lpt-disabledvet.shtml)
• Active Military Service Property Tax Deferment — A serviceperson deployed or mobilized for active service in time of war, for property owned solely by the serviceperson or jointly with a spouse/civil union partner; taxes delinquent before deployment and municipal charges such as sewer, water, and electric are not included.. Defers qualifying property tax payments during deployment/mobilization; deferred taxes are due within 90 days after deployment/mobilization ends. Yes; file Form AMSPTD and documentary proofs with the municipal tax collector; an authorized person may apply on the serviceperson's behalf. (Source: https://www.nj.gov/njbonds/treasury/taxation/lpt/lpt-activemilitary.shtml)

How to Look Up Your Property Record in Mercer County

You can look up your property's official record at https://nj.gov/transparency/property/. The official State of New Jersey Property Tax/Property Explorer lookup displays parcel information in map format, including location and block/lot information, annual assessed land and building values, prior-year taxes, and property classification; NJGIS parcel tools also allow searching by address, county, municipality, block, and lot.