Yes, I'm a U.S. citizen living in Canada. According to IRS Pub 915 pg. 6, any Social Security benefits should be reported on line 6a of Form 1040, and the taxable amount should be reported on line 6b. It also says that taxpayers residing in Canada do not pay U.S. tax on Social Security benefits. TurboTax doesn't have an interview question about this, and it calculates the taxable amount as it would for a U.S. resident. The only option I can see is to override the calculated amout on line 6b, but that obviously takes away the ability to e-file.
