How can I confirm my IRS balance due payment is pending? It is not shown up yet as a withdrawal on my account.

[DoninGA]

Call IRS e-file Payment Services 24/7 at 888-353-4537 to inquire about or cancel your payment, but please wait 7 to 10 days after your return was accepted before calling.

[DawnC]

The first page of your tax return PDF is the Filing instructions - that page will show the account and amount you have scheduled.   It normally takes the IRS a few days to take the  payment, but it is effective the date you scheduled it and confirmed by your e-file acceptance.  

See the IRS FAQ page