See this IRS website for record keeping - https://www.irs.gov/businesses/small-businesses-self-employed/how-long-should-i-keep-records
For a W-2 -
As stated on the back of the W-2 -
Keep Copy C of Form W-2 for at least 3 years after the due date for filing your income tax return. However, to help protect your social security benefits, keep Copy C until you begin receiving social security benefits, just in case there is a question about your work record and/or earnings in a particular year.
