Can I file an extension for federal if I have already e-filed and set up my payment to be deducted on April 15th?

If you have already filed the 2024 federal tax return and it has been accepted by the IRS, then filing an extension is moot.  The IRS already has your tax return and you cannot file another tax return with the same information at a later date as it will be rejected by the IRS.

You do not file an extension, you need to do an amended return to do any corrections to an already filed return. You should do this after your payment is scheduled to be done on 4/15. If your amended return shows you have overpaid on your prior return you will be given a refund.

I have my payment setup to be deducted from my checking account on the 15th. Can I amend that to be deducted at a later date?

If you change the date of payment to a later date, you will be liable for a failure to pay penalty.

Go to this IRS website for how to cancel a payment - https://www.irs.gov/payments/pay-taxes-by-electronic-funds-withdrawal

• Once your return is accepted, information pertaining to your payment, such as account information, payment date, or amount, cannot be changed. If changes are needed, the only option is to cancel the payment and choose another payment method.
• 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.
• Cancellation requests must be received no later than 11:59 p.m. ET two business days prior to the scheduled payment date.

You can make your payment after cancellation on the IRS payment website - https://www.irs.gov/payments