I thought once you were past retirement age you did not have to report you SSA benefits on your federal tax return?

Social Security Retirement/Disability/Survivors benefits are reported on a form SSA-1099 and the benefits received are to be entered on a federal tax return. The benefits may be taxable depending on the amount of other income you have entered on your tax return.
However, 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.

To enter Social Security benefits reported on form SSA-1099

Click on Federal Taxes (Personal using Home and Business)
Click on Wages and Income (Personal Income using Home and Business)
Click on I'll choose what I work on (if shown)
Scroll down to Retirement Plans and Social Security
On Social Security (SSA-1099, RRB-1099), click the start or update button

Or enter ssa-1099 in the Search box located in the upper right of the program screen. Click on Jump to ssa-1099

Up to 85% of Social Security Retirement/Disability/Survivors benefits becomes taxable when all your other income plus 1/2 your social security reaches:

• Married Filing Jointly - $32,000
• Single or Head of Household - $25,000
• Married Filing Separately - 0

If you have other income, you have to report your form SSA-1099 on your tax return.

In TurboTax Online, you can enter your form SSA-1099 by following these steps:

1. Open your tax return
2. Click on the down arrow on the right of Federal in the left-hand column, then on Wages & Income
3. Locate the section Retirement Plans and Social Security and click on the right arrow on the right
4. Click Start next to Social Security (SSA-1099, RRB-1099)​​​​​​​.