According to the CP2000 instructions, I don't need to amend my federal return, but since I have to amend my state return I entered the additional income in TT and the amount owed shows this difference...how do I know that my state amended amount owed is accurate?
What income was missing? Was there any withholding on it?
the difference is probably late payment penalties and interest. TT does not compute these. you should have gotten a notice from the IRS detailing the amount owed.
I'm not including the penalty and interest - these are just the taxed owed amounts.
I'm worried that my State amended return completed in TT is wrong if the federal amounts aren't aligned to what the IRS says I owe.
Compare the income amounts between the CP 2000 and TurboTax. The IRS probably didn't include any cost basis (of the full cost basis) when it calculated your 1099-B income, whereas you included that in TurboTax.
If that's the case, you should amend federal.
If the IRS numbers are correct, then adjust your federal amounts so they match what the IRS says and then TurboTax will update your amended state return.