Internal Revenue Service | An official website of the United States government Pay your taxes. Get your refund status. Find IRS forms and answers to tax questions. We help you understand and meet your federal tax responsibilities. Nov 13, 2020 · A one-participant 401(k ) plan is sometimes called a: Solo 401( k ) Solo- k Uni- k One-participant k The one-participant 401(k ) plan isn’t a new type of 401( k ) plan. It’s a traditional 401( k ) plan covering a business owner with no employees, or that person and his or her spouse. These plans have the same rules and requirements as any other 401( k ) plan.