My mother passed. We had a joint savings account. I re-titled after her death. The bank sent me 1099-INT for entire years interest in my SS#. How do I split?

It was yours all year if you had a joint account.

I read where you can file all of the reported interest on her return, and then claim deduction of portion after her death. Is this correct?

Since the 1099INT is in your SSN, the IRS will be looking for it on your return.  You can do a Nominee deduction and send some of it to your mothers SSN to be included on her final personal return.  I'm honestly not sure if TurboTax supports Nominee deduction in the program though.

As mentioned by SuperUser Lisa995, if the Form 1099-INT is reported under your social security number, then it should be included on your tax return.  You could then subtract a portion of the interest from your return by showing it was nominee interest.

To do so within TurboTax, use these steps to revisit the interest section of your tax return:

• On the top row of the TurboTax online screen, click on Search (or for CD/downloaded TurboTax locate the search box in the upper right corner)

• This opens a box where you can type in “1099-INT” (be sure to enter exactly as shown here) and click the magnifying glass (or for CD/downloaded TurboTax, click Find)

• The search results will give you an option to “Jump to 1099-INT”

• Click on the blue “Jump to 1099-INT” link

This will bring you to a summary of interest forms already entered.  Click Edit beside the one with the nominee amount.

After you click Continue when you have finished entering the information from your Form 1099-INT, the next screen is titled “Tell us if any of these uncommon situation apply to you”. 

The second choice on this screen is “I need to adjust my taxable amount”. 

Check this box and click Continue. 

Then you will see a screen titled “Report Interest adjustment”. 

Enter the amount as a positive number and the reason for the adjustment.  This will make the proper entry on your Schedule B.

How does this relate back to the deceased tax return? If I make the nominee adjustment under my tax return number (issued 1099-INT), do I also have to show interest split on deceased return, even though no 1099-INT was issued to that tax number?

To be technically correct, you would issue a 1099-INT to the other tax number to show the amount that you "subtracted" from your return.  Take a look at the information at the following site for more details (scroll toward the bottom to the Nominee Interest section):  <a rel="nofollow" target="_blank" href="https://www.irs.gov/taxtopics/tc403">https://www.irs.gov/taxtopics/tc403</a>