If you did not include a deduction on your 2015 return, you should amend that return - not claim it on your 2016 return.
If you used a desktop version of TurboTax software for your 2015 returns, you will be able to prepare your amended return from that software. If you used TurboTax online (Deluxe version or higher), you will be able to get the download at no additional charge with your .tax file from that year.
You can find TurboTax software from previous years at https://turbotax.intuit.com/personal-taxes/past-years-products/.
The article below has specific amendment instructions for 2015:
When you have prepared your amended return and are ready to mail Form 1040-X you should include the following forms:
- The new (amended) Form 1040
- Any forms or schedules that were added or changed as a result of preparing the amendment
Please note that 1040-X cannot be e-filed - you will need to mail a paper return. It takes the IRS at least 2 - 3 months (and sometime up to 6 months) to process amended returns. Also, depending on whether the changes affect your numbers, you may also be required to file an amended return with your state.