Qualifying for other coverage and enrolling in it can be considered a Life Event; however, the plan document of the existing policy will determine whether coverage will end on the exact date that the new policy begins or on the last day of the month in which the change takes place. Both are legal, both are common, and whichever one is determined by the plan document is set in STONE. If the plan document says that coverage on the old plan ends on the last day of the month, then it ends on the last day of the month; that is the final answer; and since the terms are available to any employee who cares to look, it cannot be considered stealing since you had access to the information ahead of time.

This is in addition to the regs regarding pre-tax refunds that Patty mentioned, and which she is more qualified to discuss than I.