Why was my 2021 tax return so far off? I received a letter from IRS stating I owe a significant amount of money.

[datmiimony-]

I filed using Turbo Tax, and also paid for upgrade. I owed money and included the payment when I filed.
I just received a letter from IRS indicating I owe more (The equivalent of triple the original amount). How could TurboTax be so far off?

[Opus 17]

We can't see your tax return or your letter.  Maybe the IRS thinks you failed to declare some income, or took credits or deductions that they don't think are allowed.  You will need to read your letter carefully.  You probably only have 30 days to reply with a defense.  

Here are some resources to get started.

https://turbotax.intuit.com/tax-tips/irs-letters-and-notices/dont-fear-the-tax-man-handling-irs-lett...

If you paid for Audit Defense when you filed, contact the company directly with the enrollment number you received. 

[NCperson]

@datmiimony- most issues relate to the Child Tax Credit and the Stimulus/ Recovery Rebate

1) what did you have on Line 28 of Form 1040?

2) what did you have on Line 30 of Form 1040?

3) what is the EXACT amount of the adjustment (before interest charges) that the IRS made?