A blackout period is a duration of time when participants cannot access their 401(k) accounts; this is typically during a time when 401(k) plan assets and records are being moved from one retirement benefit provider to another. During this time, participants will be unable to select new investments, take a loan, or make withdrawals from the 401(k) funds being transferred from the previous plan provider. A blackout period usually lasts about 10 business days.