Tax Year Prior to 2020: I filed my taxes yesterday but completely forgot to include my 1099 information. What should I do?

[KarenL2]

Once your return has been submitted for e-file, you cannot make any changes.  The IRS will not receive the change.  

Then, when/if the return is accepted, you will file a new amended return.  If your return is rejected, you can go ahead and make the change and then resubmit the e-file without filing the amendment form.

Amending is done on Form 1040X.  That form should be available for amending 2015 returns mid-February.  Also, if your return is accepted, you should not try to amend your return until it has been fully processed and you have received your refund or your payment has cleared.

Amended returns have to be printed and filed by mail.  It can take the IRS up to 12 weeks or longer to process them.   If you are due a larger refund than on your original return, your amended return should only show the difference and you will receive a separate check for it.  If you owe money on your amended return, it will show only the new amount owed, you will have to mail a check with the return.

How to Amend?

https://ttlc.intuit.com/replies/3288565

[peterkreitzer]

The amendment will show that i lost money according to my 1099 and not much only like 700$. How will that affect my return. If it causes me to lose money then obviously i will file it so i do not get in trouble. If it causes me to make more money and i do not file it can i still get in trouble.

[KarenL2]

Either way, you will need to include it because the IRS will receive a copy of it, and expect it to be on your tax return.  They will likely, eventually, send you a letter asking about it along with an estimated tax bill for it.  If you don't amend, and it causes you owe more taxes to the IRS it will create higher interest and penalties on the under-reported income.