Turbo Tax is a self prepared return. It has no way of knowing or checking that you entered something wrong or in the wrong place or entered something twice It doesn't check against any outside sources. The IRS has copies of all the W2s and 1099s your employer and banks/brokers, etc. sent in to match against. Turbo Tax only checks the calculations of what you entered. It is your responsibility to check it over before you file.
And they don't pay the extra tax, just any penalties and interest.
Do you have an amount on 1040 line 30? A common adjustment is if you claimed the Recovery Rebate Credit on 1040 line 30 when you already got the Stimulus payments or got the second one after you filed or reported the wrong amounts. Do you have an amount on line 30? And you had to report the right amount in each box. If you put the total in 1 box it would give you the other amount again. The IRS knows they already sent it to you. Line 30 is only if you qualify more.
