Twelve month period other than the calendar year, on which the employer operates it’s retirement plan.
Instead of using the calendar year, an employer may elect to use any other consecutive twelve month period as the limitation year.
This includes a fiscal year with an annual period varying from 52 to 53 Weeks. The fiscal year must satisfy certain requirements, such as the following:
The employer’s books and records must be regularly computed on the basis of an annual period which varies from 52 to 53 weeks and ends always on the same day of the week and ends always
(A) on whatever date such same day of the week last occurs in a calendar month, or
(B) on whatever date such same day of the week falls which is nearest to the last day of a calendar month,
IIRC § 441(f), Treas. Reg. §1.415-2
Additional Helpful Information
For a plan that operates on fiscal year, the deadline for making employer contributions to the plan is the due date for filing the employer’s taxable year ,including extensions
SIMPLEs cannot be maintained on a fiscal year- they must be maintained on a calendar year.