Will you be penelized for not filing a us tax return?

Yes unless you are due a refund you will be charged penalties, interest and other charges for failing to file the federal income tax return by the due date and also for failing to pay any income taxes by the due date for the income tax return.

Alternate answer:

Here is what the IRS has to say:

"Refund. Even if you do not have to file a tax return, you should file to get a refund if box 2 shows federal income tax withheld or if you can take the earned income credit."