If the taxpayer is filing married filing separately, and lived apart from their spouse the entire year, check the box 6d on Form 1040. This is marked when all of the following are true: 

• The taxpayer's filing status is 3 (married filing separately).

• Taxpayer did not live with the spouse even 1 day during the year is selected on screen 1 from the Taxpayer did not live with spouse drop list.

• Screen SSA has been entered.

In prior years, this caused a literal "D" to print beside the Social Security Benefits line instead.