1040X interest and penalties

[MGC94]

Currently taxpayers return is

-$2,474 owed fed and $19 refund state. 

Daughter is 22 and was a student and claimed herself. 

If taxpayers claimed her and her 1098t their refund would be $596 fed and $101 state. 

The daughter from claiming herself got a refund of $1,639 fed. She W/H $639. This is tax year 22. If I 1040X the return and the daughters pays back the $1,000 they would still be up $2,070 fed unless the interest and penalties is bad. 

I did the ITA and she can be a dependent. How would I even go about guessing what the daughters fees would be? 

[judys3]

Charge what you normally would to prepare the return + an amended fee.  You are having to recreate her return 

[MGC94]

@judys3 I mean IRS fees not my fee

[TaxGuyBill]

I don't THINK penalties apply. 

The interest rate is currently 8%.  It has been a bit over a year, so the interest on a $1000 would be roughly $100, probably a little more.

If I am wrong and the failure-to-pay penalty applies, that would approximately double it (another $100, probably a bit less).

I can't think of anything else that would apply.