Employee removes dependent from health plan in error–can it be fixed?

Q: “Regarding a High Deductible Health Plan (HDHP) with a Health Savings Account (HSA): Under what circumstances may a correction be made if an employee removed a dependent from a medical plan in error? For example, with an HDHP, the employee or a spouse may also be covered by Medicare, but may not contribute to the HSA, per IRS regulations. Our employee received a letter from the company stating this after the spouse became eligible for Medicare. The employee interpreted this information to mean the spouse must be removed from the HDHP medical plan. During open enrollment, the employee removed the spouse from medical insurance. After the fact, the employee realized this error/misunderstanding. Changes like this may call into question the Section 125 plan. What are the options for a situation like this—can the spouse be added back to the insurance?” - Patty, Washington