"In general, 401k plan records must be kept for a period of not less than six years after the filing date of the IRS Form 5500 created from those records. However, records necessary to a participant's claim for plan benefits must be kept ... 'as long as a possibility exists that they might be relevant to a determination of the benefit entitlements of a participant or beneficiary.' This can mean indefinitely. Some of the most common plan records a 401k sponsor must retain are itemized [in this article]."