A Practice Note providing an overview of the one-participant 401(k) plan, also known as a solo 401(k), single participant 401(k), or individual 401(k) plan. It discusses the eligibility requirements, steps to starting and maintaining a plan, contribution limits, treatment of distributions, tax treatment, and key features. The Practice Note identifies the advantages and disadvantages of the one-participant 401(k) plan and considerations for a small employer.