is my social security income taxable if am over 70

Yes no age limit.   Up to 85% of Social Security 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

To see the Social Security Benefits Calculation Worksheet  in Turbo Tax Online version you would have to save your return with all the worksheets to your computer.   Or if you are using the Desktop CD/Download Software you can switch to Forms Mode (click Forms in the upper right) and click on SS in the list on the left side.

Your age has nothing to do with whether your Social Security is taxable.   Your SS can be taxable if you have other kinds of income in addition to the SS.   If Social Security is your ONLY income, you do not have to file a tax return.

Up to 85% of your Social Security benefits can be taxable on your federal tax return.  There is no age limit for having to pay taxes on Social Security benefits if you have other sources of income along with the SS benefits.  When you have other income such as earnings from continuing to work, investment income, pensions, etc. up to 85% of your SS can be taxable. 

 What confuses people about this is that before you reach full retirement age, if you continue working while drawing SS, your benefits can be reduced if you earn over a certain limit. (For 2021 it was  $18,960.  For 2022 it was  $19,560  —  for 2023 $21,240)  For 2024, $22,320.  For 2025 it will be $23,400

After full retirement age, no matter how much you continue to earn, your benefits are not reduced by your earnings; your employer will still have to withhold for Social Security and Medicare.  If you work as an independent contractor then you will pay self-employment tax for Social Security and Medicare.

To see how much of your Social Security was taxable, look at lines 6a and 6b of your 2024 Form 1040

https://www.irs.gov/help/ita/are-my-social-security-or-railroad-retirement-tier-i-benefits-taxable

You need to file a federal return if half your Social Security plus your other income is

Single or Head of Household      $25,000

Married Filing Jointly                  $32,000

Married Filing Separately            $0

Some additional information:  There are 9 states that tax Social Security—Colorado, Connecticut, Kansas, Minnesota, Montana, New Mexico, Rhode Island, Utah, and Vermont  These states offer varying degrees of income exemptions, but two mirror the federal tax schedule: MN and VT.