IRS notice CP14 after filing and paying full amount

[pirahna67]

I received IRS notice CP14. I filed on 10/7/22 (had an extension), paid the full amount TT said to pay and now the IRS says I owe interest. If I really do owe interest, why didn't TT have me pay it when I filed? 

[VolvoGirl]

Turbo Tax can't know the amount of interest.  It is calculated by the IRS when they receive your payment.   It's common for the IRS send a bill for interest.  Do you have an amount on 1040 line 38?  Ev3n if you do it is only an estimated amount.  

[Critter-3]

The extension was for more time to file the return but the estimated taxes owed were due back in April.  So if you didn't pay the balance due until you filed you do owe interest for the late payment and a possible failure to pay penalty and the IRS/state each  bills you for what they calculate you owe based on when they get the payment.    The TT program only calculates the estimated underpayment penalty until the 4/15 filing deadline. 

[pirahna67]

Yes I do. The tax notice showed the amount on line 38 as the penalty and then an additional amount for total interest.

[pirahna67]

Good to know. I paid my best guess before the 4/15 deadline but still came short apparently.