I missed a w2, but already filed. what do I do?

[AdrianL]

You must file an amended 2016 tax return to include information that was missed.  

However, we recommend that you wait to amend until after the IRS has processed your original return and you have received your refund (if any). It's possible the IRS will adjust your return for the missing W2, in which case you will not need to amend your return. This happens fairly often for unreported income.

If you do need to amend, the form needed to amend your 2016 tax return will be available after February 11, 2017. 

Once the form is ready, TurboTax can help you file the amendment.  To learn more about amending your tax return, please review the information in the following link and the Frequently Asked Question included below.
Do I Need to Amend?

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