By January 31, 2013, most employers had to include the value of their health care coverage in Box 12 of the W2.  Cobra reporting should include the actual cost, not including 2% premium charges. 

Below is a quick reference guide for employers:

Form W-2 Reporting of Employer-Sponsored Health Coverage
Form W-2, Box 12, Cod DD
  Coverage Type: Report Do Not
Report
Optional
Major Medical  x    
 Dental or vision plan not integrated into another medical or health plan      x
 Dental or vision plan which gives the choice of declining or electing and paying an additional premium      x
 Health Flexible Spending Arrangement (FSA) funded solely by salary-reduction amounts    x  
 Health FSA value for the plan year in excess of employee’s cafeteria plan salary reductions for all qualified benefits  x    
 Health Reimbursement Arrangement (HRA) contributions      x
 Health Savings Arrangement (HSA) contributions (employer or employee)    x  
 Archer Medical Savings Account (Archer MSA) contributions (employer or employee)    x  
 Hospital indemnity or specified illness (insured or self-funded), paid on after-tax basis    x  
 Hospital indemnity or specified illness (insured or self-funded), paid through salary reduction (pre-tax) or by employer  x    

Reference: HR Daily & SHRM.org