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Just in case, How to submit documentation for accuracy guarantee claims.
Is your Social Security 0 on 1040 line 6b?
What usually happens is the IRS changed some other income on your return. Like the taxable amount of a 1099R you got or you missed entering some income. Like if a 1099R got entered on the wrong line 1040 line 4 or 5, the IRS would miss it and think you didn’t report it. By increasing your other income it made more of your SS taxable.
Or There is a new question this year asking if you lived in a foreign place. People have been answering it wrong or skipping it. Go back through the Social Security entries.
See this thread that has a screenshot
https://ttlc.intuit.com/community/retirement/discussion/re-tax-on-social-security/01/3613956#M245879