YOu can not amend a return more than three years back, for several reasons.
1) TurboTax only supports their program for the current tax filing season and three years back. In order to amend a prior year return you *MUST* use the CD/Desktop version of the TurboTax program that you physically install on your Windows or MAC computer. For tax years 2015 and back, the *REQUIRED* updates and corrections for the program are no longer availalble. So if you use TurboTax to amend a 2015 return or older, it *will* *be* *wrong* most likely.
2) The IRS says that if amending a return more than three years back will result in you getting a refund, you *WILL* *NOT* be paid that additional refund. Three year statute of limitations on that. However, if you owe the IRS, you *WILL* pay what you owe, plus interest, penalties and late fees.
First, confirm beyond "any" doubt that you have not taken depreciation on the property. With the exception of some scenarios, the TurboTax program figures depreciation "for you" in the background and does not bother you with the details. So look at your 2018 tax return and pull up the SCH E. If there's a figure on line 18 under the column for that specific rental property, then depreciation was taken for 2018.
To confirm it's been taken all years, save the 2018 tax return in PDF format and you want to save everything. Not just the "forms required for filing" or the "forms for you records." You want to save *EVERYTHING*. Then open the PDF and look for two IRS Form 4652's related to that specific property. Both forms will print in landscape format. One is titled "Depreciation and Amortization Report" and the other is "Alternative Minimum Tax Depreciation". You're interested in the first one.
On that form 4562 you'll see the property listed as an asset. If you have numbers in that row in the "prior years depr" column it's probably 5 times or more the amount in the "current year depr" column and indicates that you have "in fact" been depreciating the property all along without even realizing it.
Now if you have not been depreciating the property, then the bottom line is, you need to seek professional help to fix this. While the TurboTax program does include the IRS Form 3115, it *is* *not* *simple* as it may look, or as you may think. If you yourself are not a tax professional, then you need to seek the services of a tax professional to help you with this. Since you have not taken depreciation for more than 3 years back, amending is not an option for you. The 3115 is required in order to fix this. Seek professional help yesterday, if not sooner.
