I owe PA $3.00 state tax. Who should the check be payable to and where do I send the check? Also, should I mail anything else with the check?

Make the check/money order payable to: PA Department of Revenue

Please mail the PA-V and your payment to:

PA Department of Revenue
Payment Enclosed
1 Revenue Place
Harrisburg, PA 17129-0001

The state voucher should have printed with your state return. 

If not, you can return to "Your tax returns & documents" on the Home Page and print the voucher or use the link below for the State of Pennsylvania. 

"You can download the PA-V form from our website.  You can also write the last four digits of your Social Security number, "2016 PA-V", and daytime telephone number on your check or money order. If you are filing a joint return, enter the last four digits of the SSN shown first on your return. The department will need the last four digits of your SSN to accurately apply your payment."

https://revenue-pa.custhelp.com/app/answers/detail/a_id/245/related/1/session/L2F2LzEvdGltZS8xNTU0ODIzMzUyL3NpZC9ObjhMVlBibw%3D%3D