There is no requirement that your Social Security Benefit Statement (SSA-1099) itself be "attached," either physically or electronically, to your federal tax return, but it does need to be entered into TurboTax so that the amount of the benefits will be present on Form 1040 line 6a and the taxable portion, if any, will be present on line 6b. That doesn't mean that the IRS can't subsequently ask you for a copy, particularly if the amount on line 6a does not match the records provided by the SSA to the IRS.
