I filed my Federal taxes correctly as a Non-resident using 1040NR-EZ form, and I had to pay a certain amount. I paid online using payusatax.com (on-time) but used the "pay 1040 balance due" option. I made a mistake in assuming it covered all 1040 forms.
The money got debited, and I got a confirmation number, too. 2 months after, I got a notice from IRS saying I haven't paid my taxes and I need to pay it by a certain date with a penalty.
How do I rectify this mistake? Will I need to pay it again, or will IRS be able to redirect it properly?
Thanks in advance.