To change an LLC from a sole proprietorship to a partnership, you add a second owner, sign a multi-member operating agreement, file an amendment with your state, apply for a new EIN from the IRS, and switch your federal tax filing to Form 1065. The moment a single-member LLC takes on a second member, the IRS treats the old “disregarded entity” as terminated and a new partnership as created, and the steps below follow from that reclassification.
Draft a Multi-Member Operating Agreement
Before you touch any government form, put the deal in writing between you and your new co-owner. The operating agreement is the private contract that governs how the LLC runs, how money moves, and what happens when someone wants out. It is not filed with the state, but it is the document that keeps a partnership from falling apart at the first disagreement.
Ownership, Contributions, and Profit Splits
List every member and their ownership percentage. Percentages usually track what each person contributes, whether that is cash, property at an agreed value, or services. Spell out exactly what is coming in and what stake it buys.
Then state how profits and losses get divided. Profit splits do not have to match ownership percentages. An LLC can allocate 60% of profits to a member who owns 50%, as long as the arrangement has a legitimate business purpose. Each member gets a separate capital account tracking contributions, allocations, and withdrawals. If those accounts are not maintained under the IRS partnership rules, the IRS can throw out your allocations and reassign income by ownership percentage instead.
Management and Voting
Decide whether the LLC will be member-managed, with every owner involved in daily decisions, or manager-managed, with designated managers running operations while other members stay passive. Write down voting rights, which decisions need a supermajority or unanimous vote, and who is responsible for what.
Exit Provisions
The clauses people most want to skip are the ones that matter most. Buy-sell provisions should explain how a departing member’s interest gets valued and bought out, what triggers the buyout (voluntary withdrawal, death, disability, bankruptcy), how the price gets set (independent appraisal, formula, or agreed value), and how it gets paid (lump sum or installments). Also cover what happens if the LLC dissolves entirely and how remaining assets and debts get handled.
File an Amendment With Your State
Once the agreement is signed, update the LLC’s formation documents with the state. That usually means filing an amendment to the articles of organization (called a certificate of formation or certificate of organization in some states) with the Secretary of State’s office.
The form asks for the LLC’s legal name, its state filing number, and a description of the change. Some states also require the names and addresses of new members. Most states post the form on the Secretary of State website and accept online filing; others still require a mailed paper form.
Fees generally run between $25 and $150 depending on the state. Online filings often clear in a few days, while mailed filings can take a few weeks.
Apply for a New EIN
Your existing EIN belonged to the disregarded entity, and the IRS treats that entity as terminated the moment a second member joins. The new partnership needs its own EIN before it can file federal taxes, open accounts, or run payroll.1Internal Revenue Service. When to Get a New EIN
The fastest path is the free online application at IRS.gov/EIN, which issues the number immediately. You will need a valid Taxpayer Identification Number (usually a Social Security number) for the “responsible party,” plus basic details about the partnership. If the online tool will not work for you, file Form SS-4 by fax or mail and expect several weeks of processing.2Internal Revenue Service. Instructions for Form SS-4
Close Out the Sole Proprietorship on Your Taxes
For the part of the tax year before the conversion, the original sole owner files a final Schedule C with their personal Form 1040, reporting business income and expenses up to the date the partnership began.3Internal Revenue Service. Closing a Business Use the original EIN on that final return. That closes the books on the disregarded entity.
File as a Partnership Going Forward
Starting from the conversion date, the multi-member LLC files Form 1065, U.S. Return of Partnership Income. The partnership itself pays no federal income tax. It is a pass-through entity, so income, deductions, gains, and losses flow through to the members.4Internal Revenue Service. About Form 1065, US Return of Partnership Income
With Form 1065 the partnership prepares a Schedule K-1 for each member showing that member’s share of income, deductions, and credits. Each member then reports the K-1 figures on their personal Form 1040. Whatever profit split you wrote into the operating agreement is what shows up on each K-1.
Deadline and Late Penalty
Form 1065 is due March 15 for calendar-year partnerships, or the 15th day of the third month after the tax year ends for fiscal-year partnerships. Filing Form 7004 gets you an automatic six-month extension, pushing calendar-year filers to September 15.5Internal Revenue Service. About Form 7004, Application for Automatic Extension of Time to File Certain Business Income Tax, Information, and Other Returns
Missing the deadline is expensive. The penalty is $255 per partner for each month or partial month the return is late, up to 12 months. A two-member LLC that files three months late owes $1,530. The bill grows with the number of partners.6Internal Revenue Service. Instructions for Form 1065
Exception for Married Couples
If the only two members are spouses who both materially participate and file a joint return, they may be able to elect “qualified joint venture” status, skip Form 1065, and each file a separate Schedule C on the joint return. Eligibility can depend on state law and how the LLC is classified, so a married couple forming a two-member LLC should confirm with a tax professional before assuming full partnership filing applies.7Internal Revenue Service. 2025 Instructions for Form 1065 – US Return of Partnership Income
Know the Tax Consequences of the Contribution
A common worry: does the new member owe tax on the value of the ownership interest received, and does the existing owner owe tax on property rolled into the partnership? Usually no. Federal law provides that neither the partnership nor any partner recognizes gain or loss when property is contributed in exchange for a partnership interest.8Office of the Law Revision Counsel. 26 US Code 721 – Nonrecognition of Gain or Loss on Contribution
A contributing member’s tax basis in the new partnership interest equals cash contributed plus the adjusted tax basis of any property contributed. So $50,000 in cash plus equipment with a $20,000 adjusted basis creates a $70,000 starting basis. The partnership takes over the contributor’s basis in the property rather than stepping it up to fair market value.9Office of the Law Revision Counsel. 26 USC Subtitle A, Chapter 1, Subchapter K, Part II, Subpart A Those basis figures matter later when the partnership sells the contributed property or a member sells their interest.
Plan for Self-Employment Tax
A member’s share of LLC income is generally subject to self-employment tax, not just income tax. The rate is 15.3%, made up of 12.4% for Social Security and 2.9% for Medicare, and it applies once net self-employment earnings reach $400 for the year.10Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes)
The Social Security portion applies only up to an annual wage base. For 2026 the cap is $184,500 in combined wages and self-employment income.11Social Security Administration. Contribution and Benefit Base Earnings above the cap still face the 2.9% Medicare tax, which has no ceiling. High earners may also owe an additional 0.9% Medicare surtax on self-employment income above $200,000 for single filers or $250,000 for joint filers.
If you were already the sole owner, self-employment tax is not new. It will be new to a member joining from a W-2 job, and the first quarterly estimate can be a shock. Budget for it from day one.
Update Everything Else
The legal and tax filings get most of the attention, but the administrative cleanup after conversion is longer than most people expect. Once the new EIN and amended articles are in hand, work through these items in the first few weeks:
- Bank accounts. Take the new EIN, amended articles, and operating agreement to your bank. Most will either update the existing account or require a new one under the partnership’s EIN, and you will need to update authorized signers.
- Business licenses and permits. City, county, and industry licensing boards typically require notice when ownership changes, and some charge a fee to update the license. Missing that notice can put the permit at risk.
- Contracts and insurance. Check existing contracts for change-of-ownership clauses; some require written consent from the counterparty. Insurance policies deserve special attention because an ownership change can affect coverage.
- State tax registration. If your state has an income tax, register the partnership for state filing. Many states have their own partnership information return and annual fees.
- Payroll and 1099 accounts. If the LLC has employees, update federal and state payroll accounts with the new EIN. Send updated Form W-9 information to any clients who issue you 1099s.
Keeping a written checklist and working through it methodically will save you from tracking down a missed registration during tax season, when the partnership return itself is already competing for your attention.