You need to provide more details in order to get a *correct* useful response. There are to many assumptions that can be made here.
It is a commercial building.
Let's see if this helps, and I can only hope it's not dead wrong for your explicit and specific situation, whatever that situation may be.
Since it's commercial rental property (or was) then it was set up to depreciate over 39 years using straight line depreciation. (residential rental property depreciates over 27.5 years). If you are changing from renting the property out to a third party, and will be using it for your own business, the depreciation schedule remains at 39 years straight line. Basically, you're just switching it from SCH E to whatever schedule is used for your business. What specific schedule is used depends on the type of business - be it a partnership, multi-member LLC, S-Corp or C-Corp.
To close the rental property out on the SCH E simply indicate that the property was "sold or otherwise disposed of". Note that you also have to indicate this in the Assets/Depreciation section of the SCH E also. Then when asked if special handling is required, indicate YES. If you select NO, then it's assumed you sold the property and you will be "FORCED" to enter asset sales information. For the date you stopped using it as rental property, that must be at least one day after the last renter moved out.
Then for making it commercial business property, you will indicate your acquisition of the property *EXACTLY* the same as you did on the SCH E. When asked when the property was placed "in service" it must be the exact same date it was placed in service on the SCH E.
Then you will be presented a figure for "prior year's depreciation already taken". This number must match the total depreciation taken on the property up to the day you took it "out of service" on the SCH E. Otherwise, you will be "double dipping" on the current year depreciation amount and that will raise flags at the IRS.
