Retirement tax questions

May 2025. I reviewed my completed 1040 with on-line TT.  I saw line 6a SSA-1099 amount with zero taxable. TT calculated a big refund. Why would I question you?  IRS sent a letter with some SS taxable and a bill plus interest! TT live call said he would check and call me back. A brief text reply from him said I answered a question that I lived in a foreign country that is why no SS was taxed.  He said I should call Max Audit. They are only for IRS audits.  HUH. I cannot find a worksheet for line 6a.  

Your old answer to this thread says we do not need to calculate taxable amounts because TT does it for us.