You must include all of your income from 2016 on your return, even if the amount is not a large amount. There is a chance that the IRS might catch the error and recalculate your return with the missing W-2 income. If that is the case you will be informed of the changes the IRS makes to your return by mail.
Since you have already filed your return, you'll need
to wait for your tax return to either be rejected or accepted, if it is rejected you can add your Form W-2, correct any other
errors on the return and resubmit it. If it is accepted, you will need to amend your return to include the
Form W-2. Please be aware that Form 1040X will not be available to
prepare in TurboTax until mid-February, but once it is available, you will be
able to prepare and print your amended return so that you can mail it to the
IRS. You can not e-file an
amended return as this cannot be filed electronically. The form is only
filed on paper, so it will need to be printed and filed by mail.
Please see the following TurboTax FAQ for instructions on how to amend your 2016 tax
return in TurboTax.
https://ttlc.intuit.com/replies/3288565
