Referring to a duplex, please confirm.
Assuming you owned the duplex for more than 5 years (you didn't specify) by "reported separately" do you mean to day that one side was your primary residence for the entire time you owned it?
What about the other side? If you haven't rented it out for the last four years, then would I be correct in assuming that you took physical action on the prior year tax return for whatever year, to convert it back to personal use?
Regardless of your response here, there are a few forms you will need from the tax return of the last year you reported rental income/expenses on SCH E.
First, you will need both IRS Form 4562's. They both print in landscape format. One is titled "Amortization and Depreciation Report" and the other is "Alternative Minimum Tax Depreciation".
The other form you will need is the IRS Form 8582 which shows your passive loss carry overs. If you don't have a form 8582 then that's okay. That just means you don't have any passive loss carry overs. But that would not be common with rental property.