This proposed solution does not work for the 2018 tax year (tax returns due in 2019). It interferes with the calculation of taxable social security benefits and consequently, the amount displayed on Form 1040 Line 5b. Turbo Tax should provide (on the Social Security Income input screen) a 'tick box' for people with Social Security income that is exempted under Article 17 of a Tax Treaty.
I have resorted to reporting both the income and the exempted amount on line 21 of Schedule 1 like this: US Social Security: $1,234 and US Social Security exempt from tax per US/UK Tax Treaty Art 17, Part 3: $-1,234.
