What do i do if i already filed my w2 but forgot that i had a ira withdrawal earlier in the year that i didnt include?

[peckhamjesse]

I didn't include my 1099-r when I filed. What penalty will I have? How do I fix this?

[Texas Roger · Accepted solution]

You should not have a penalty if you file the amended return before the April 18 filing deadline.

If your return is rejected by the IRS, you can correct the problem and fix the reason for rejection and re-efile your return. If your return is accepted by the IRS, you must prepare, print, sign and mail an amended tax return form 1040X to correct the problem. 

DO NOT change your original tax return until you start the amended return. If you have already changed it from the way it was originally filed and accepted, you must change it back before you start the amended return. Wait until you receive the refund from your original return before beginning your amended return to make sure you enter the correct amount. An amended return cannot be efiled. Here is an FAQ to help you:                                                                  

https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed