What does the code C mean on line 12 of the W2 form?

On line 12 of the W-2 form, the code "C" refers to "Taxable cost of group-term life insurance over $50,000." This amount is considered taxable income and must be reported on the employee's tax return. Employers use this code to indicate the value of the benefit provided that exceeds the tax-exempt threshold of $50,000.