ADU Tax Depreciation: What Orange County Rental Owners Need to Know in 2026

Quick answer: You can depreciate an ADU only if you rent it out. The structure depreciates straight-line over 27.5 years starting on its placed-in-service date, and finishing construction before December 31 instead of January can let you claim a year of depreciation sooner. A personal-use ADU, like a primary-residence remodel, is never depreciated.

If you're building an accessory dwelling unit and planning to rent it out, one question comes up almost every time: can you depreciate an ADU on your taxes? The rules for a rental ADU are specific, and getting the timing right can meaningfully change how much you deduct in your first tax year. If you haven't priced out the project yet, our ADU cost guide breaks down typical costs by type and size, and if you're still deciding between an ADU and a traditional addition, see how the two compare.

Depreciation only applies to income-producing property. If you rent out your ADU, whether as a long-term lease or a separate unit listed on its own, the IRS treats it as residential rental real property and lets you depreciate the construction cost over time. If the ADU is for personal use only, such as a home office, guest space, or space for a family member who doesn't pay rent, there's no depreciation to claim. That distinction determines everything else in this article.

Once an ADU is placed in service, meaning it's built, permitted, and ready for a tenant, its structure depreciates on a straight-line basis over 27.5 years under the IRS's General Depreciation System for residential rental property. A $150,000 ADU, for example, generates roughly $5,455 in annual depreciation deductions on the structure alone. The clock starts on the date the unit is actually available to rent, not the date construction wraps up on paper, so a certificate of occupancy and a genuine listing or lease matter for documentation.

Under the One Big Beautiful Bill Act, 100% bonus depreciation is now permanently restored for qualifying property placed in service after January 19, 2025. It's a meaningful benefit, but it doesn't apply the way most people assume. The ADU's structure itself, as 27.5-year residential rental property, doesn't qualify for bonus depreciation. What does qualify are components with a shorter recovery period: appliances, carpeting, certain fixtures, and specific electrical or plumbing components tied to those items. Identifying which parts of an ADU fall into those shorter categories typically requires a cost segregation study, which is worth a conversation with a CPA to see if the extra analysis pays for itself in year-one deductions.

Because depreciation starts on the placed-in-service date, finishing your ADU before December 31 instead of in early January can be the difference between claiming a partial year of depreciation now or waiting until next year's return. It also lines up with the most practical time to build: fall and winter are typically the slower season for contractors in Orange County, which usually means more availability and better pricing than the spring rush. Planning a build to wrap up by year-end isn't just a scheduling preference. For a rental ADU, it can be a real financial one.

This is general information, not tax advice. Every situation is different, and a CPA or tax attorney can confirm how these rules apply to your specific return (see IRS Publication 527 for the full framework on residential rental property). What we can help with is the construction side: building a licensed, permit-ready ADU in Orange County on a schedule that gets it placed in service when you need it to be. Contact CRS Construction at (714) 486-2472 to talk through your ADU project and timeline.