Or make an online payment at <a rel="nofollow" target="_blank" href="
http://www.irs.gov/payments">www.irs.gov/payments</a>. You don't need the paper voucher because you will use your SSN on the online site to link the payment to your tax account. You can use direct bank debit (for free) or a credit card (for a service charge). Just be sure to select "2016 form 1040" as the reason for the payment (and not 2015 back taxes or 2017 estimated taxes.)
