Can I cancel or amend a pending return?

No, you can't cancel or amend a pending e-filed return.

Submitting your e-filed return is like dropping it in the mailbox. It enters pending status until it's either accepted or rejected by the IRS.

You can amend your return once it's accepted. If your return gets rejected, you won't need to amend it. You can just fix your return, make your changes, and resubmit it.