Do you need a “study” to use the tax benefits of cost segregation?

Of course not.

Will hiring a firm to create a cost segregation study report improve the strength of your cost recovery bookkeeping?

Of course.

Will a cost segregation study report help you in the event of a tax audit?

Possibly, but real‑world experience indicates that depreciation methodology and documentation of this are challenged in only a small portion of Schedule E audits involving rental property. There are valid methods other than a cost segregation study to defend this type of audit.