if the return was submitted then you will get an acceptance or rejection e-mail. if rejected you can finish it and resubmit. if accepted, you have created a hassle for yourself. you'll now have to wait until the return is processed - you receive your refund or the IRS takes your payment. then you'll have to submit an amended return 1040-X to include whatever was omitted. if there's a state return that's accepted you may need to amend it also. it depends on what was omitted.
