What each document is for
Stubs explain each paycheck to the employee. The W-2 reports annual wages and withholding to the employee, the IRS and the Social Security Administration.
How they connect
W-2 box 1 is wages after pre-tax deductions such as a traditional 401(k). Boxes 3 and 5 are Social Security and Medicare wages, which do include 401(k) contributions.
Deadlines
Employers must give W-2s to employees and file them with the SSA by January 31.