Cost segregation studies differ in two ways: the method used to assign costs, and the situation they're done for. The IRS considers detailed engineering-based studies the most reliable and rule-of-thumb estimates the least. Studies are also tailored for new purchases, new construction, renovations, or look-backs on property you've owned for years.
This content is not tax or financial advice for you. Please talk with a CPA to find what's right for your situation.
Studies by method
The IRS Cost Segregation Audit Techniques Guide describes several common approaches. Here's how they stack up:
| Method | How it works | Reliability | Best for |
|---|---|---|---|
| Detailed engineering, actual costs | Uses real construction invoices and records, component by component | Highest | New construction with good records |
| Detailed engineering, cost estimate | Engineer inspects and estimates costs using industry cost data | High | Purchased buildings |
| Residual estimation | Values the short-life items; the rest is assigned to the building | Moderate, if done carefully | Smaller or simpler properties |
| Sampling or modeling | Applies data from studied properties to similar ones | Moderate, depends on statistics | Large portfolios of similar buildings |
| Survey or letter | Relies on owner or contractor statements | Low | Rarely recommended |
| Rule of thumb | Applies a fixed percentage | Lowest | Avoid relying on it |
Studies by situation
Acquisition study
For a building you just bought. The provider estimates component costs since you don't have construction records. This is the most common type for investors.
New construction study
For a building you built. Actual cost records allow very precise allocations. Ideally, the provider gets involved during construction to capture details before walls are closed up.
Renovation or improvement study
For major upgrades. It sorts new improvements into short and long lives and can identify old components you removed. Those removed parts can often be written off through a partial asset disposition.
Look-back study
For property you bought in a past year without a study. Using Form 3115, you catch up all the missed depreciation in the current year without amending past returns.
Portfolio study
For owners with many similar properties. Sampling or modeling may reduce cost, but it must follow sound statistical methods.
Full study vs. lighter options
Some providers offer lower-cost reports for small properties, often based on a virtual tour and residual estimation. These can make sense for a modest single-family rental. Just know the tradeoff: less detail means more exposure if the IRS questions the numbers.
How to pick the right type
- Match the method to the stakes. Bigger deductions deserve a more detailed method.
- Use what records you have. Construction invoices make an actual-cost study possible.
- Think about timing. Bought this year? Do an acquisition study. Bought years ago? Do a look-back.
- Plan for renovations. Get a study when you renovate so you can write off removed components.
Frequently asked questions
Is an engineering-based study required?
Can I do a study years after I bought the property?
Can one study cover several properties?
See what your property may qualify for
Run our 2-minute STR Qualification Quiz or model your Low / Mid / High cost segregation range.
Related guides
IRS Cost Segregation Requirements: What a Quality Study Must Include
The IRS spells out what a quality cost segregation study looks like. Use this plain-English checklist to judge a study before you rely on it.
Read guideWhat Is a Cost Segregation Study? How It Works, Costs, and Savings
Learn what a cost segregation study is, how engineering reports reclassify 5-, 7-, and 15-year property for 100% bonus depreciation, and who benefits most.
Read guideForm 3115 for Cost Segregation: Catch Up Missed Depreciation Without Amending
Form 3115 lets you claim years of missed depreciation in one year, without amending returns. Learn how it works with look-back cost segregation studies.
Read guideDIY Cost Segregation: Can You Do It Yourself?
Thinking about DIY cost segregation? Learn what's allowed, the risks, how software options compare, and when doing it yourself makes sense.
Read guideThis content is not tax or financial advice for you. Please talk with a CPA to find what's right for your situation.