Is there a way to amend my taxes from being submitted before the IRS starts accepting them?

No. After you click Transmit Returns Now, your e-file goes to pending status, where it will stay until it's either been accepted or rejected by the government.

Think of pending as "in transit" or "in limbo" – just like you can't cancel a letter that you sent yesterday, you can't cancel a return that's on its way to the government.

To make corrections or changes to your pending return, wait until your return's either been accepted or rejected.

• If your return gets accepted, you'll need to amend (please note that the ability to amend will not be available until mid-February, please do not attempt to amend before then). 
• If your return gets rejected, you'll be able to make your changes before you re-submit your return.

For more information on situations that require and amendment please see this FAQ:  https://ttlc.intuit.com/replies/3318732