When you file your federal or state tax return by mail, you will attach your W-2 to the tax return.
If you e-file your tax returns, it is not necessary to mail in your W-2s.
If you forget to attach your W-2 to your mailed in return, you should wait until the IRS (or your state Department of Revenue) contacts you for additional information. They will send you a letter requesting the documents. You should attach the documents to a copy of that letter and mail the information back.
Please feel free to post any additional details or questions in the comment section.
