Cost Segregation Study in Delaware for Airbnb and Short-Term Rental Investors

Delaware has long been what tax practitioners call a rolling-conformity state: its personal income tax code (Title 30 of the Delaware Code) generally follows the Internal Revenue Code as currently written, without a separate state depreciation table for owners to maintain. That changed for bonus depreciation specifically when House Bill 255 amended Title 30 to decouple from OBBBA's full-expensing provision. For individuals and pass-through owners - S corporations, partnerships, and sole proprietors, which is how most rental property is held - the decoupling applies to property placed in service after December 31, 2025, effective for tax years beginning January 1, 2026, covering eligible property placed in service through December 31, 2030. Delaware's corporate income tax decoupled on an earlier trigger (property placed in service after January 19, 2025), but that corporate track is separate from what applies to individual owners and most rental LLCs taxed as pass-throughs.

During the 2026-2030 window, Delaware doesn't disallow accelerated depreciation outright - it requires an add-back on the state return and a recomputation of depreciation using the rules that applied immediately before OBBBA's bonus-depreciation provision took effect, which reflects the pre-OBBBA bonus percentage that was already scheduled to phase down toward zero after 2026. The Delaware Division of Revenue published Technical Information Memorandum 2025-02 on December 23, 2025, addressing the HB 255 decoupling, though investors should confirm current filing mechanics and any subsequent form-level instructions with a CPA before relying on any specific procedure. In practice, the add-back targets the bonus percentage itself, not the shorter 5-, 7-, and 15-year recovery periods a cost segregation study assigns to building components. That means a study still compresses depreciation into fewer years than the standard schedule even for a post-2025 Delaware purchase - it just may not deliver the full first-year state deduction that a 2025 placed-in-service date would.

None of this changes what makes holding real estate in Delaware attractive in the first place: Tax Foundation places Delaware's average effective property tax rate on owner-occupied housing value at roughly 0.54%, among the lowest in the country and well below neighboring Pennsylvania, New Jersey, and Maryland - though county-level rates vary meaningfully, running lower in Sussex County (home to the beach rental markets below) than in New Castle County. Lower carrying costs leave more of a property's cash flow available to reinvest, and a cost segregation study's savings compound against that already-favorable expense base rather than being offset by heavy property tax overhead.

Standard IRS depreciation tables treat a residential rental building as one asset, written off in equal amounts over 27.5 years (39 years for commercial property), regardless of what's actually inside it - flooring, cabinetry, appliances, decking, parking areas, and landscaping all get lumped in with the structure. A cost segregation study is an engineering-based analysis, typically involving a site visit and detailed construction-cost documentation, that separates those components out and assigns each one the shorter recovery period the tax code actually allows: 5 years for items such as appliances and certain flooring, 7 years for furniture and fixtures, and 15 years for land improvements like driveways, fencing, and exterior lighting. Under the One Big Beautiful Bill Act, signed into law in July 2025, that reclassified 5-, 7-, and 15-year property qualifies for 100% federal bonus depreciation when the underlying property is acquired after January 19, 2025 - meaning the entire reclassified amount can be deducted in the year the property is placed in service instead of spread out year by year. For a newly purchased or recently renovated Delaware property, that front-loaded deduction can meaningfully offset rental income in the first year of ownership, subject to the Delaware-specific add-back described above for property placed in service starting in 2026.

For illustration only — your results depend on your property and tax situation, and this is not a projection of actual savings.

Consider an investor who buys a $650,000 short-term rental cottage near Bethany Beach and places it in service in November 2025, before Delaware's decoupling window begins. After allocating roughly 20% of the purchase price to land ($130,000), the depreciable basis is about $520,000. A cost segregation study might reclassify around $145,000 of that basis into 5-, 7-, and 15-year property - the deck, exterior lighting, driveway, certain flooring, and furnishings. Because the property was placed in service in 2025, both the federal and Delaware returns allow 100% bonus depreciation on that reclassified $145,000, rather than spreading it across decades under the standard schedule. Now compare an otherwise identical property placed in service in March 2026: the federal return still gets the full 100% bonus on the reclassified amount, but the Delaware return would require an add-back, recomputing that portion under the slower pre-OBBBA schedule and pushing more of the state-level benefit into later years. These are illustrative, round numbers only - actual land allocations, component values, and applicable tax brackets vary by property and by owner.

Investors who bought or renovated a Delaware rental years ago haven't missed the window. A 'look-back' cost segregation study can be performed on a property that's already in service, and rather than filing amended returns for every prior year, the correction is made through IRS Form 3115, Application for Change in Accounting Method. That filing triggers a Section 481(a) adjustment, which lets the owner claim the full amount of depreciation that should have been taken in prior years as a single catch-up deduction in the current tax year. For a Delaware owner who has held a beach rental or a Wilmington-area long-term rental for several years without ever separating out the building's components, a look-back study can surface a substantial one-time deduction without reopening old filings.

• Short-term rental and Airbnb hosts operating in Rehoboth Beach, Dewey Beach, Bethany Beach, Fenwick Island, or Lewes, where beach-season demand drives strong rental income
• Long-term rental property owners in Wilmington, Newark, Dover, and other New Castle and Kent County markets
• Investors who purchased or substantially renovated a Delaware rental property recently, especially near the December 31, 2025 / January 1, 2026 dividing line that determines Delaware's bonus depreciation treatment
• High-income W-2 earners or business owners exploring the short-term rental material participation strategy, which uses the seven-day-or-less average guest stay test to potentially treat STR losses as non-passive
• Owners of multiple Delaware rental units who have never had a cost segregation study performed and may benefit from a look-back analysis