Alternatively known as a Solo-k, Uni-k and One-participant k, the solo 401(k) plan is designed for a business owner and his or her spouse.

Because the business owner is both the employer and employee, elective deferrals of up to $22,500 can be made in 2023, plus a non-elective contribution of up to 25 percent of compensation up to a total annual contribution of $66,000 for businesses, not including catch-up contributions of $7,500 for 2023.