FSA Participant Deferrals that fall outside the plan year

[AnneD]

Can FSA Deferrals fall outside the Plan Year?

For example. in a 1/1/15 - 12/31/15 Plan Year, is the employer permitted to take the final deferral in the 1/5/16 pay check (for pay period ending 12/31/15)?

Where is this cited in the Regs?

Thank you!

Anne