How do I add an explanation to my return?

you can't include a written explanation in an e-filed return.? what is the reason it's wrong? we may be able to suggest a workaround. your other choice is to mail in your return and hope an agent actually reads the explanation. 

My mother passed away at the end of October and the 1099's I have been getting include the full year, but her return is only supposed to be until the date of her death.  I asked an accountant friend of mine and he said he files the amount from the 1099 and then adjusts it to the correct amount and includes a note that it has been adjusted and that the adjusted amounts will be included in the estate's 1041 return

You can use the nominee procedures which will allow you to show the portion that belongs to others and then report only your portion of the interest income.

Nominee Interest: Some or all of the interest belongs to someone else but the entire amount was reported under your Social Security number. This includes interest belonging to other beneficiaries but reported under your ID number.

In TurboTax you do this by entering the 1099-INT, then checking on the next screen that you need to adjust the amount. You'll then be able to enter the adjustment amount and check the reason for the adjustment.

Thanks for the answer.  When I read your answer I slapped myself because I had actually used the nominee option about 5 years ago.  Thanks

I would think using the nominee option would require an indication of who received the adjusted amount, in this case, the 1041 return, EIN ###.  Where does Turbotax allow additional explanation?

There is no place on the tax return to add an additional explanation for that situation.  If you want to add further documentation you would print and mail the return with copies of the 1099s that you want to include and an explanation of the nominee status.

@JCla