If the Social Security benefits is the Only income to be reported on the tax return and there is no federal income taxes being withheld, then there is no reason or need to file a tax return..
Unless you also received a Form 1095-A for your health insurance through one of the State Marketplace Exchanges or from healthcare.gov then you must file a tax return.
If your only income is Social Security then there would be nothing from which to receive a refund unless you are having tax withheld from the SS benefits during the year. If SS is your only income, you will not be required to file a federal tax return unless you have marketplace health insurance and receive a 1095A.
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