How much tax do I owe if my social security was my only income?

[DoninGA]

If the Social Security benefits are the Only income to be reported on the tax return, then there is no reason or need to file a tax return.

However, if you have healthcare coverage through one of the State Marketplace Exchanges or from healthcare.gov and receive a Form 1095-A then you must file a federal tax return.

[VolvoGirl]

Or if there was tax withholding from SS you need to file to get it refunded.  To efile you might need to enter $1 of bank interest.  You can make up a 1099Int.  It won't affect your return but let you efile.