Each tax year, you may be required to fill out Form 5500, depending on the type of plan you choose. This form of individual retirement account is available to owner-only businesses, freelancers, and businesses with very few employees.401(k) plans can be a powerful tool to promote financial security in retirement. How to choose, maintain and fix plan errors of a retirement plan for the selfemployed. Benefits of setting up a plan. All tax credit forms should be filed in the name of the single member. LLC but included with the owner's return. Solo 401(k) plans are not limited to sole proprietorships. The only thing you need to set up a Solo 401(k) is an Employer Identification Number, or EIN, to prove that you own a legitimate business. No income from investments in the LLC can go into your personal accounts.