The easiest way to get a copy of your W-2 is through your employer. All you have to do is ask and they should be willing to supply you with a copy of your W-2 for the most recent year or for past years, depending on your needs.
If that isn't an option, you can also request a copy of a past tax return directly from the IRS. Unfortunately, you can't request your W-2 on its own. Instead, you have to request your entire tax return, which will include any W-2s that were submitted. The main downside to going this route is that you will need to pay a fee in order to get a copy of your return. As of 2015, that fee is $50.00 for every past year's tax return that you request. Here are the steps that you will need to follow:
1. Go to the IRS website and download Form 4506, Request for a Copy of Tax Return (available here - https://www.irs.gov/pub/irs-pdf/f4506.pdf
2. Fill out the form, being sure to include the year(s) for which you are requesting the return. Keep in mind that you will have to pay a $50.00 fee for each year that you request. This could add up quickly if you need more than one year.
3. If the tax return needs to be sent to a third party, include their mailing information on the correct line. For instance, sometimes banks or mortgage companies will want a copy of your tax return.
4. Sign the bottom of the form and submit it to the IRS, using the mailing address that is provided in the instructions for the form.
5. Once the IRS receives and processes the form, they will mail copies of your return to you or to the third-party address that you specified.
Alternatively, if you don't need a paper copy of your W-2, but instead just need to see the income information that was printed on it, you can view it online for free by requesting a transcript. A transcript provides a line-by-line listing of all of your tax information for a particular year. You can view information from the past 10 years online by requesting a transcript here:
This video does a great job of showing you how to go about obtaining a transcript directly from the IRS: