Underpayment penalty -Paying directly ?

[reverse]

So I filed my taxes but forgot to pay $5 underpayment penalty.

Can I pay @ https://www.irs.gov/payments right now to avoid any sort of notice from IRS ?

Do i need to file amended return ?

[VolvoGirl]

You don't pay that separately.  It was included in your tax due.  

[dmertz]

And if the IRS determines a higher penalty, they will bill for the difference.  If the IRS determines a lower penalty, they will refund the difference.

[VolvoGirl]

Oh yeah, 1040 line 24 says Estimated underpayment penalty and is included in line 23.  Notice that line 23 is more than line 16-19.  Or you can even have a penalty when you are getting a refund.  I did once.  

[reverse]

will they bill even for $5 ?

[reverse]

my main question was -

Can I pay @ https://www.irs.gov/payments right now to avoid any sort of notice from IRS ?