NO, you cannot retrieve an already-efiled return to make any changes to it. The IRS starts processing returns on January 28 (except for a few that are pulled early for testing purposes.) You'll need to wait until then (or a couple days after due to the backlog) to see if your return is accepted or rejected, unless the IRS pulls your return early.
If your return is rejected, you can make any changes at that time and resubmit the efile.
If your return is accepted, then to make any changes you'd need to prepare a formal amended return Form 1040X and associated forms.
In the meantime, do NOT make any changes in your return in case you need to amend it. If you do need to amend, it must start off exactly it was when originally filed.
An amended return cannot be efiled. It has to be printed and mailed, and can take the IRS up to 16 weeks to process.
If you have to amend your Federal return, you may have to amend the State return as well.
If you have to amend, and you are due a Federal refund, then wait until you get the refund before preparing the amended return.
