You have options for payment. An amended return must be mailed, it will not be filed electronically. If you are saying you have not yet received acknowledgement for your original return, wait to file the amendment because your return could get rejected which would mean you have the ability to correct it and send it back through e-file again.
You can fill out and print a 1040-V to send with your payment or you can make your payment online with the IRS. You can create an account if you like and if you don't have one already,
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