The following video was published by the IRS.
What if you want to file your tax return but you still don’t have your W-2? Employers should send this to you by January 31. Give it a few weeks to arrive in the mail, but if you don’t get it by the end of February, the first thing you should do is check with your employer. If you moved, make sure they have your new address.
If you don’t get your W-2 on time, you must file anyway. Good news is you can use Form 4852 instead of your W-2. List your estimated wage and withholding on the form. You can use a pay stub, or similar statement to help estimate the amount. If later on you receive your W-2 and discover that your estimate was off, you’ll have to correct your tax return. Do this by filling out Form 1040x. Keep in mind that your amended return can take up to 16 weeks to process.
Finally, if you tried to get your W-2 from your employer and you still haven’t received it by the end of February, you may call the IRS and they will send a letter to your employer.