When you invest using your Solo 401(k), the party you are investing with will often ask you to complete IRS Form W-9, Request for Taxpayer Identification Number and Certification. In some cases, the same information is requested within a separate document such as a partnership subscription agreement or investor questionnaire.
The W-9 tells the income issuer how to report payments to your plan. Completing it correctly ensures that income is reported to the tax-sheltered Solo 401(k), not to you personally.
Your Solo 401(k) is a retirement trust with special tax treatment under the IRC. The plan has its own EIN, obtained as part of the setup process, which identifies it to the IRS as a tax-sheltered retirement plan. Income reported to that EIN is understood by the IRS to belong to the plan, not to you personally.
Line 1 — Name
Enter the full name of the Solo 401(k) plan. Use the exact name shown on your plan's EIN confirmation letter. This is typically formatted as: [Business Name] 401(k) Plan.
Line 2 — Business name / Disregarded entity name
Leave this blank. The Solo 401(k) has no disregarded entity layer.
Line 3 — Federal tax classification
Check the box for "Other" and write in "401(k) Retirement Plan."
Part I — Taxpayer Identification Number
Enter the Solo 401(k) EIN in the Employer Identification Number field.
Part II — Certification
Sign and date as you normally would. You are signing as the plan trustee and administrator.
[SAMPLE W-9 IMAGE - Solo 401(k) as taxpayer]
Why don't I use my personal Social Security Number?
Your Social Security Number identifies you as an individual taxpayer. Using it would cause income to be reported to you personally rather than to the tax-sheltered Solo 401(k). The plan EIN exists for exactly this purpose.
Why don't I use my business EIN?
Your business EIN identifies your operating company, not the retirement plan. Using the business EIN would direct income reporting to your taxable business rather than to the tax-sheltered plan. The Solo 401(k) has its own separate EIN for this reason.
What if a subscription agreement asks similar questions but is not a W-9?
Many investment sponsors use their own investor questionnaires or subscription agreements in place of a standard W-9. The IRS recognizes these "W-9 equivalent" documents as acceptable for taxpayer identification purposes. Answer the fields the same way you would a W-9: the Solo 401(k) plan is the taxpayer, Line 2 is left blank, and the TIN is the plan EIN.
Where can I find my plan EIN?
Your plan EIN is listed on the first page of your plan adoption agreement. You should also have received a CP-575 letter from the IRS when the EIN was issued.
This information is provided for educational purposes only and should not be interpreted as tax, legal, or investment advice. Readers are encouraged to consult a qualified professional who can offer guidance based on their personal situation.