Based on your summary it appears that the employer did make a binding commitment to reimburse employees for the cost of alternative coverage in the event they were not able to remain in the group health plan. Since these reimbursements would be taxable, they would not fall under the 409A exception for non-taxable benefits. As such, I believe this commitment would fall under Section 409A the payment of a lump sum in lieu of the ongoing reimbursement would be an impermissible acceleration. Since this commitment relates to their prior employment status, I believe the taxable amounts would be reported on Form W-2, Box 12, using Code Z. It is not necessary to withhold for the additional 20% excise tax.