Employer-sponsored health insurance primarily affects your income taxes in two ways - First, it helps meet the requirement that you have health insurance and second, it reduces your taxable income if your portion of the premiums (if any) is paid for with pre-tax earnings (payroll deductions).
If your Form W-2 reports an amount in Box 12, Code DD (Cost of employer-sponsored health coverage), that means you paid your part of the insurance premiums with pre-tax earnings.
