IF prepared properly in the software, with correct account numbers, it will get debited and posted sometime this week....(And will not be late if the 18th was selected, assuming you filed on time)
A Gazillion people selected auto-debit on 18 April....and the IRS (and state if applicable) sometimes take a few extra days to actually get it posted.
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A printout of your Tax return with the Federal or State Electronic filing Instructions sheet (there are separate forms for each) will show the account numbers and date you entered.
Many states do not allow you to arrange a Direct-Debit with your e-file, and you have to pay them separately from your tax return filing.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*