I am a US and Canadian citizen living in Canada. Under Tax Treaty my Social Security is taxed in Canada and exempt in US.
On my US return I can enter my benefit but I cannot figure out how to make it exempt.
Report the income in the social security section of your tax return (to satisfy the IRS), then make an adjustment on the line 21 of the 1040. Select Less Common Income, Miscellaneous Income, Other Reportable Income. Enter a description, then a negative number. From the IRS link below.
Claiming Tax Treaty Benefits | Internal Revenue Service
If a tax treaty between the United States and your country provides an exemption from, or a reduced rate of, withholding for certain items of income, you should notify the payor of the income (the withholding agent) of your foreign status to claim the benefits of the treaty. In addition, you should complete Form 8833 Treaty-Based Return Disclosure, and attach it to your 1040.