So what did the IRS change? Read the whole letter over slowly and carefully. It will say. What CP# or Letter # is at the top?
1040 Line 43 is taxable income. They probably increased that one. And common things they increase income is for 1099R income. Either you missed entering one or you reported the wrong taxable amount on line 15b or 16b. Or it showed up on the wrong line 15/16 so the IRS missed it. And if you get Social Security and they increase some other income it will make more of your SS taxable.
