Source:
https://www.irs.gov/uac/Pay-Taxes-by-Electronic-Funds-Withdrawal
To cancel your payment you can go to the IRS website linked above. Scroll down to "Cancellations, Errors and Questions."
It will tell you how to phone "IRS efile Payment Services" and cancel.
It says to wait 7-10 days after it's accepted before you call.
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