New Castle County homeowners pay a median of $2,499 a year in property tax on a median home value of $352,200. Its effective tax rate (property taxes paid as a share of home values, per the Tax Foundation) is 0.72%, the highest of 3 Delaware counties. The New Castle County Office of Finance, Assessment Division values every home in New Castle County at its market value as of the last countywide reassessment (finished for 2025 tax bills). Appeals go to the New Castle County Board of Assessment Review.
Opens soonAll 2026 deadlines have passed (Kent January 30, New Castle March 14, Sussex March 15). Next deadlines: Kent by 5 p.m. Friday, January 29, 2027 (Kent's FAQ says January 31; the earlier date is the safe one); New Castle before March 15, 2027; Sussex's filing period usually opens in mid-January and closes March 15 (2027 dates were not posted on the Sussex board page when checked).
Each county has its own fixed yearly deadline, and the filing must be received, not just postmarked. New Castle County: file before March 15 (in 2026 the county set the deadline as March 14, 2026). Kent County: the appeal must reach the Assessment Office by 5:00 p.m. on the last working day of January (January 30, 2026; next is Friday, January 29, 2027). Kent's FAQ and credits page say January 31, so use the earlier date; the deadline can change in reassessment years. Sussex County: the 2026 filing period ran January 12 to 4:30 p.m. on March 15, 2026; postmarks were not accepted. An appeal filed in a given year affects the tax bill for the tax year that starts that summer (June 1 in Kent). In Kent, if the county raises your value mid-year with a supplemental (quarterly) assessment, you have 30 days from that notice to appeal.
Phone: 302-395-5520
Email: [email protected]
Address: 87 Reads Way, New Castle, DE 19720
Official website: newcastlede.gov
This office keeps your property record, sets your assessed value, takes appeal forms and can fix errors in your home's details.
Official website: newcastlede.gov
Hears appeals of the value. Check its filing window and rules.
In a reassessment year every owner gets a notice of the new value. In other years there is no annual notice: the county publishes a newspaper notice saying where to look up assessments and when to appeal. If the county raises your value outside a general reassessment (for example, after new construction), it must send you written notice at least 10 days before the change.
Look up your home on the New Castle County Office of Finance, Assessment Division website and check square footage, bathrooms, condition and features. Mistakes are the easiest wins. Use our record card checklist.
File the county's written appeal form, one per parcel, with all your evidence, so it is received by New Castle County's yearly deadline (postmarks are not accepted in Kent or Sussex). In Kent and Sussex an assessor may try to settle it first; otherwise the appeal goes to a hearing.
At least 3 arm's-length sales of similar homes near the base date (Sussex and Kent: sales from January 1, 2021 to June 30, 2023; New Castle: roughly 2022 to mid-2024); An appraisal valuing the home as of the base date. New Castle requires a Delaware-licensed appraiser; in Kent and Sussex the appraiser must attend the hearing to testify; Your own purchase price and date, if you bought in an open-market sale near the base date; Photos showing condition problems.
You must prove your home's assessment is higher than its fair market value on the county's base date, using evidence filed with your appeal. In Superior Court the Board's decision is presumed correct: you must show the Board acted contrary to law, fraudulently, arbitrarily or capriciously, and your evidence must be sufficient to show a substantial overvaluation (9 Del. C. § 8312(c); the 'substantial overvaluation' test comes from case law, Fitzsimmons v. McCorkle (Del. 1965), quoted in Burroughs v. Kent County Assessment Office (Del. Super. May 15, 2025)).
Next step: Delaware Superior Court (in your county). Within 30 days (by postmark) after you receive the Board's written decision. File an appeal in the Superior Court for your county. The Board sends the court its hearing record within 20 days, and the court mostly reviews that record, though it may allow new evidence. The court can affirm, reverse, change or send back the decision; its decision is final. Court filing fees apply; check with the Superior Court Prothonotary.
Enter the market value on your assessment notice and what you think the home would really sell for. We estimate the yearly saving if the board agrees with you.
Some states cap how fast the taxable value of a home can rise (California, Florida, Michigan and Texas homesteads, for example). If your taxable value is already held below market value by a cap, a lower market value may not lower this year's bill.
Fill in your details and download a written appeal statement as a PDF or Word file. Most boards also require their own appeal form: file the form and attach this letter and your evidence to it.
Tax Appeal Map is a free information site, not a law firm or appraiser. The letter is a template, not legal advice.
Each county has its own fixed yearly deadline, and the filing must be received, not just postmarked. New Castle County: file before March 15 (in 2026 the county set the deadline as March 14, 2026). Kent County: the appeal must reach the Assessment Office by 5:00 p.m. on the last working day of January (January 30, 2026; next is Friday, January 29, 2027). Kent's FAQ and credits page say January 31, so use the earlier date; the deadline can change in reassessment years. Sussex County: the 2026 filing period ran January 12 to 4:30 p.m. on March 15, 2026; postmarks were not accepted. An appeal filed in a given year affects the tax bill for the tax year that starts that summer (June 1 in Kent). In Kent, if the county raises your value mid-year with a supplemental (quarterly) assessment, you have 30 days from that notice to appeal.
File a written appeal with the New Castle County Board of Assessment Review through the New Castle County Office of Finance, Assessment Division, by mail, in person or online/email where offered. If you lose, you can appeal to the Delaware Superior Court within 30 days (by postmark) after you receive the decision.
Phone 302-395-5520. Website: newcastlede.gov.
No filing fee appears on the Kent or Sussex forms. New Castle calls the process free (Town Square Delaware, Feb. 2026).
Contact details change; call or check the office website before you visit.