Remember that an extension does not give you more time to pay. You need to pay your tax due by April 15. The extension only gives you more time to prepare and file your tax return forms.
https://turbotax.intuit.com/irs-tax-extensions/
https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-extension/need-file-extension-person...
You will need to ask your employer about the federal withholding amount in box 2. Did you give them a W-4? Maybe you did not ask for enough to be withheld? Or...depending on your filing status and on whether you have dependents, perhaps they only needed to withhold a small amount. If, for instance, your filing status is Head of Household, they would not have withheld much for the amount you earned.
W-4
https://turbotax.intuit.com/tax-tools/calculators/w4/
https://www.irs.gov/individuals/tax-withholding-estimator
https://www.irs.gov/pub/irs-pdf/fw4.pdf
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
