Employers must report all employer and employee Health Savings Account (HSA) contributions made through payroll as a single aggregated amount on the employee’s form W-2 in Box 12 using code W.

If an employee has an amount reported in box 12 of their Form W-2 (Code W) for employer contributions to your health savings account (including contributions through a cafeteria plan), then the employee should complete IRS form 8889 Health Savings Account.