New Castle County discovers new property tax errors, moves up next reassessment

Why Should Delaware Care? Assessed property values are the foundational piece of how property taxes are assessed for homeowners and commercial property owners. After values were reset for the first time in 40 years, many New Castle County property owners decried the impact that the new values had on their property.

New Castle County intends to reassess every property in northern Delaware a year earlier than previously planned after a recent audit of a sampling of commercial properties found an abundance of errors.

County Executive Marcus Henry made the announcement Thursday in a statement sent out alongside the audit report.

Completed by real estate firm Cushman & Wakefield, the report examined 50 commercial properties whose valuations went down more than the median following the 2024 reassessment — or were lower than a recent sale.

The report highlighted a variety of what investigators called discrepancies, including misstated building sizes, inaccurate property classifications, and even erroneous room counts for hotels and apartment buildings.

One shopping center was found to have been classified as an office building.

The findings are likely to fuel concerns raised early this year when the county separately corrected assessment errors on several large properties, including an Amazon fulfillment center near Newport, and apartments and a parking garage in downtown Wilmington.

David Del Grande, the county’s chief finance officer, attributed the errors in the latest report, in part, to New Castle County’s failure for decades to reassess properties. He also pointed to missing permitting data from municipalities, including the city of Wilmington.

Assessors from Tyler Technologies — the contractor hired to complete the reassessment — also conducted only exterior examinations of properties, and relied upon county data for information about the interiors.

Further, only about 1% of commercial property owners responded to surveys asking for updated information about their properties prior to the reassessment. Del Grande said the surveys could have provided information about income that commercial properties produce, among other details.

Finally, Del Grande noted that the reassessment took place at the same time that New Castle County was switching out its appraisal software.

“It could have been data that was in the wrong field coming from the old system to the new system. It could have been data overridden by Tyler in the new system. It could be a variety of things,” he told Spotlight Delaware.

A tortured reassessment process

The recent findings, as well as the county’s decision to push forward the next reassessment, mark the latest in two years of acrimony that followed New Castle County’s first-in-a-generation property reassessment.

The results of the reassessment initially sparked outrage from many homeowners whose property tax bills spiked, while the tax liabilities for some business properties dropped. Lawmakers responded in 2025 by enacting several pieces of legislation, including one bill that allowed New Castle County and its area school districts to charge a different tax rate for business and residential properties.

The new split tax rate subsequently sparked a legal challenge from apartment owners. The Delaware Supreme Court ultimatelyultimately upheld the tax structure last year.

Still, concerns around the accuracy of business property valuations continued this year prompting lawmakers to authorize the inquiry of New Castle County business properties.

The inquiry ended with Thursday’s report.

“From the beginning, we wanted an independent review because we needed to know where improvements were necessary,” Henry said in a statement.

What’s next?

Next, county officials will develop and then advertise a new request for contractors to submit bids to conduct the next property reassessment.

County officials are targeting July 2028 as their date for completing the base property assessments – one year earlier than previously planned.

Those assessments would then appear on 2029 tax bills, according to the county.

Del Grande said the next reassessment will again be completed by a third-party vendor, and that nothing in the latest audit findings would preclude Tyler Technologies from bidding and being considered by the county.

If completed on time, the earlier reassessment would be completed ahead of the 2028 elections, when Henry could be on the ballot.

Editor-In-Chief Jacob Owens contributed to this story.

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