@Yonah Weiss thanks for the tag.
@Hiro Kitagawa, qualified improvement property has become a bit more interesting than your CPA made it out to be.
Now, there is in fact a category for owners of non-residential real property called qualified improvement property (QIP) that as of 1/1/18 replaced the old qualified improvement property (yes, same), qualified leasehold improvement, qualified retail improvement, and qualified restaurant property classification rules, as well as includes some property that would not have fallen into those buckets previously.
The committee reports indicated that QIP placed in service on or after 1/1/18 would be eligible for a 15-year depreciable life as well as bonus depreciation rather than the standard 39-year, non-bonus eligible method applied to non-residential real property.
However, the law was not drafted correctly, i.e., there was a technical error, and the section of the tax code describing 15-year property (Section 168(e)(3)(E)) was in fact not amended to include qualified improvement property.
So for now, strictly-speaking, in 2018, qualified improvement property is regular old 39-year property that is not eligible for bonus depreciation.
We do expect that a technical correction to the law will be made, but for now the IRS has actually stated that it cannot guarantee that absent legislative correction it will accept the legislatively intended change in recovery period and bonus eligibility.
Anyway, this is neither here nor there since you have stated you are a landlord of residential rental property rather than non-residential real estate.
And this does not affect the application of 100% bonus depreciation to both qualifying new and used property place in service after 9/27/17 and before 1/1/23 that @Yonah Weiss pointed out.