The IRS allows you to pay for certain benefits on a before-tax basis providing you with a tax savings on the cost of coverage. In return for this tax savings, the IRS restricts your ability to make changes to before-tax benefits.
Your before-tax benefit elections must remain in effect throughout the calendar year unless you have a qualified family status change that necessitates a coverage change. The change in your benefits coverage must be due to and consistent with the qualified family status change.