Since e-filing for the 2017 tax season has been permanently closed by the IRS, that means you have to print, sign and mail your tax return. So you can send a check with the return if you want. Otherwise, you can also pay online at http://www.irs.gov/directpay. If you need to pay state taxes also, then you'll have to check your state's department of revenue website to see what options they offer. Not all states offer online payment of taxes due.