How do I stop the return once it's sent?

Once you have transmitted your returns, you cannot stop them. 

You will need to wait to see if your return is accepted or rejected. If rejected, you may correct and resubmit. If it is accepted, you will need to file an amendment.

Please reference  this TurboTax FAQ  for how to amend.

Please remember:

An amended return, Form 1040X, can only be printed and mailed to the IRS, it cannot be e-filed.

Three weeks after you mailed your amendment, you can start tracking its progress at the IRS Where's My Amended Return? site.

Before starting to amend the tax return, wait for the tax refund to be received or the taxes due to be paid and processed by the IRS.

• You're free to cash your refund check or spend it once you have it. You don't need to wait for your amendment to finish processing, which can take another 3-4 months.
• If you owe money after amending, you'll just include payment with your mailed amendment form.
• And if your amendment results in a second refund, you'll get a check for the additional amount.

 The IRS will take 16 weeks or longer to process an amended tax return.