MMC Benefits Handbook
Claims Filing Deadline
The claims filing deadline is March 31 following the end of the plan year. For example, for the 2019 plan year, your eligible expenses must be incurred no later than December 31, 2019 and must be submitted to the Claims Administrator by March 31, 2020 (the claims filing deadline).
Expenses are treated as having been incurred when the care or service is provided, not when you are billed or pay for it.
The plan year is January 1 through December 31.