Hi cap51, thank you for joining TurboTax Special Forum today.
Having Social Security withholds income tax just one way to pay in some tax to offset overall tax liability when you file tax year 2021 tax return. The goal is not to have a large balance due and not to incur estimated tax penalty.
Depending on other income, Social Security benefits can be no tax, or partially taxable up to 85% of the value.
TurboTax has an Income Tax Calculator (TaxCaster) to assist with estimated refund/balance due.
https://turbotax.intuit.com/tax-tools/calculators/taxcaster/
If you like to pay in some tax, IRS Direct Pay is a convenient way for estimated tax payment.
https://www.irs.gov/payments/direct-pay