Why Should my 401(k) Plan Use a Calendar Plan Year?

Defined contribution plans generally follow calendar years, which prevents compliance and administration complications that arise from an off-calendar plan year. Off-calendar plan years are typically structured to follow the fiscal year, with the rationale that the profit sharing contributions would be tied to fiscal year performance. This logic is somewhat flawed, since you are effectively giving the same profit sharing contribution at whatever point you decide to make the contribution, but you are increasing the administrative costs and risk of errors (administration or compliance) in running the off-calendar plan year.