If you want to challenge your new valuation in Delaware, you file a formal property tax reassessment appeal with your county’s Board of Assessment Review by the county’s deadline: the last working day of January in Kent County, March 14, 2026 in New Castle County, and March 15 in Sussex County. Miss the date and you lose the right to contest that year’s assessment. Everything else about a Delaware property tax reassessment appeal, from the evidence that persuades a board to the relief programs you should check at the same time, works around that deadline.
Why Your Assessment Changed
In 2020, the Delaware Court of Chancery ruled in In re Delaware Public Schools Litigation that all three counties were taxing property based on values decades out of date: 1974 in Sussex, 1983 in New Castle, and 1987 in Kent. The court found this violated the state’s True Value Statute and the Uniformity Clause of the Delaware Constitution, because two homes worth the same amount could carry very different tax bills depending on when each was last assessed.1Justia Law. In re Delaware Public Schools Litigation (2020)
Kent County completed its reassessment for the 2024 tax year. New Castle County’s new values apply to the 2025 tax year, and Sussex County began billing on new values for fiscal year 2026. Kent and Sussex used a valuation date of July 1, 2023; New Castle used July 1, 2024.2Sussex County. Sussex County Reassessment3New Castle County, DE – Official Website. Assessment Those valuation dates matter when you appeal, because the question in front of the board is what your property would have sold for on that specific date, not today.
A higher assessment doesn’t automatically mean a higher bill. State law requires counties to calculate a “rolled-back rate” that would raise the same revenue as the prior year, and all three counties have indicated they do not plan to collect above that rate.4Justia Law. Delaware Code Title 9 Section 8002 – Tax Rate But reassessment redistributes the tax burden. If your home’s value rose by more than the county average, your share of the total levy grows even when the rate drops. That is often what prompts an appeal.
Appeal Deadlines by County
Each county runs its own calendar, and the deadlines are strict.
- Kent County: Annual appeal forms must be received by the Assessment Office no later than the last working day of January, by 5:00 PM. Postmarks are not accepted. Supplemental and quarterly billing appeals have separate deadlines throughout the year.5Kent County. Kent County Board of Assessment – Property Assessment Appeal Procedures
- New Castle County: The deadline for formal appeals for the 2026 tax year is March 14, 2026. You can file online or submit the residential or non-residential appeal form to the Board of Assessment Review.6New Castle County, DE – Official Website. Board of Assessment Review
- Sussex County: Applications for property assessment appeals must be submitted by March 15.7Sussex County. Sussex County Accepting Applications for Property Assessment Appeals
Fill out every field on the form. Include your opinion of the property’s value and attach your supporting documentation when you file. An incomplete form can be dismissed on technical grounds before anyone looks at your evidence.
Try an Informal Review First
Before you commit to a formal appeal, check whether your county’s informal review window is still open. Each county offered an informal review period after mailing assessment notices, giving property owners a chance to flag factual errors such as wrong square footage, missed condition issues, or an incorrect property classification. Staff review the request and correct clear mistakes without a hearing.8Kent County Levy Court. An Open Letter to Kent County Property Owners
Informal review is faster and less adversarial. If the problem is a data entry error, this is the place to fix it. In Kent County, owners unsatisfied with the informal result could request a preliminary hearing before escalating to the Board of Assessment Review.
Evidence That Wins an Appeal
The burden is on you to show that your assessed value exceeds what the property would have sold for on your county’s valuation date. The strongest single piece of evidence is a recent independent appraisal from a certified appraiser, ideally one dated close to that valuation date.
Comparable sales come next. Look for homes that sold near the valuation date and that match yours in size, location, age, and condition. County assessment databases list recent sale prices, so you can pull the figures yourself. The closer the comparable, the more weight it carries.
Document physical defects that reduce market value. Foundation problems, an aging roof, outdated electrical or plumbing systems, and flooding history are all relevant. Take clear interior and exterior photographs. If the county’s records show wrong square footage, incorrect lot size, or a use classification that doesn’t match reality, bring documentation of the correct figures. These clerical errors are often the easiest wins.
What doesn’t help: arguing that your tax bill is too high, that the increase from last year is unfair, or that you can’t afford to pay. The board decides value, not affordability.
What Happens at the Hearing
Once you file, the Board of Assessment Review schedules a hearing and notifies you of the date, time, and location by mail.5Kent County. Kent County Board of Assessment – Property Assessment Appeal Procedures You present your evidence to a panel that decides whether the assessment should be adjusted. New Castle County hearings are held at the Government Center, 87 Reads Way, in New Castle.6New Castle County, DE – Official Website. Board of Assessment Review New Castle County received more than 5,200 formal appeals from this reassessment, so expect scheduling to take time.9New Castle County, DE – Official Website. Reassessment Project Information
The board may not announce a decision on the spot. Either way, you’ll receive written notification by mail. If the board agrees the assessment is too high, it orders the assessment office to reduce the value to the figure the board sets.
If you disagree with the board’s decision, the next step is an appeal to Delaware Superior Court. That’s a formal legal proceeding, and most owners who go that far work with an attorney. The full escalation path runs from informal review to preliminary hearing (where offered) to the Board of Assessment Review to Superior Court.
While Your Appeal Is Pending
Filing an appeal doesn’t stop a tax bill from coming due. For New Castle County residents, the General Assembly passed House Bill 247, which requires the county to offer payment plans for county and school property taxes on residential properties for the 2025–2026 tax year. You get at least 30 days from the date of the offer to enroll. While you remain in compliance, the county cannot charge fees, penalties, or interest on the taxes owed and cannot take collection action, including a lawsuit or tax sale. The law sunsets on December 31, 2026, but protections continue for payment plans that extend past that date as long as you keep paying.10Delaware General Assembly. House Bill 247
If you pay through a mortgage escrow account, expect your lender’s annual escrow analysis to raise your monthly payment to cover the new tax amount and to catch up any shortage from the prior year. You can usually pay the shortage as a lump sum instead of spreading it across 12 months. If your assessment dropped, the analysis works in reverse and you may see a refund or lower payment.
Relief Programs to Check Alongside Your Appeal
Even if your reassessed value is accurate, you may qualify for relief programs that reduce the bill. Apply for these on their own tracks; they are separate from the appeal process.
Senior School Property Tax Credit
Homeowners 65 or older can receive a credit equal to 50% of their regular school property taxes, up to $500. Apply by April 30 each year with a valid driver’s license or state ID. You must also have paid the prior year’s property tax bill in full to remain eligible.11Department of Finance – State of Delaware. Senior School Property Tax Relief
Disabled Veterans School Tax Credit
Veterans with a 100% VA disability rating can receive a credit covering 100% of non-vocational school district property tax on their primary residence. You must have held legal domicile in Delaware for at least three years. Applications are due April 30 and require a valid ID, documentation of your VA disability, and a copy of your Social Security card. You cannot claim this credit and the senior school property tax credit in the same year.12Department of Finance – State of Delaware. Disabled Veterans School Tax Credit
County Homestead Exemptions for Seniors
Each county offers its own homestead exemption that reduces taxable assessed value. The rules differ:
- Kent County: You must be 65 by May 31 and have been a Delaware resident for five consecutive years before the tax year. The property must be your principal residence for at least 12 months before applying.
- New Castle County: You must be at least 65 before July 1 of the applicable fiscal year and have been domiciled in Delaware for 10 consecutive years. The maximum exemption reduces your assessed value by up to $173,000.
- Sussex County: You must be 65 by April 30 and have been a full-time Sussex County resident for at least five years. The maximum exemption reduces your assessed value by up to $229,000.
Contact your county’s assessment office for application forms and documentation requirements. After reassessment, these exemptions can take a meaningful bite out of what you owe, whether or not you also appeal.