My US LLC Has More Than One Owner. What Do We File by September 15?

A US LLC with two or more owners is treated as a partnership by default, which means it files Form 1065 and issues a Schedule K-1 to each owner. If you requested an extension in the spring, that return is due September 15, 2026. This is a different form and a different deadline than the single-owner track most non-resident guides describe, and missing it carries a penalty measured per owner, per month.

If your company has partners abroad, this is the deadline that applies to you, not the October one. Here is what is actually due, what it costs to be late, and where the single-owner rules stop applying.

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01Why Does a Two-Owner LLC File a Partnership Return?

The moment a US LLC has more than one owner, the IRS treats it as a partnership unless you formally elected to be taxed as a corporation. A partnership does not pay income tax itself. Instead it files an information return, Form 1065, that reports the company's income and then passes each owner their share on a Schedule K-1. Each owner reports that share on their own return.

This is the fork that trips up founders who read the usual non-resident advice. That advice is almost always written for the single-owner LLC, which is a disregarded entity and follows a completely different path. Add a second owner and the return, the form, and the deadline all change.

02How Is This Different From the Single-Owner Form 5472 Deadline?

A single-owner foreign-owned LLC is disregarded for tax and files a pro-forma Form 1120 with Form 5472 attached, due October 15 on extension. A multi-owner LLC is a partnership and files Form 1065 with K-1s, due September 15 on extension. Same country, same LLC wrapper, but a full month earlier and an entirely different filing.

• One owner: disregarded entity, pro-forma 1120 plus Form 5472, extended deadline October 15.
• Two or more owners: partnership, Form 1065 plus a Schedule K-1 per owner, extended deadline September 15.
• Elected to be taxed as a corporation instead: Form 1120, its own rules, also October 15 on extension.

03What Does Filing Late Actually Cost?

The late-filing penalty for a partnership return is charged per owner, per month, not as a single flat amount. It runs roughly $245 for each owner for every month or part of a month the return is late, for up to twelve months, and the IRS adjusts the figure each year. A two-owner LLC that files three months late is looking at well over a thousand dollars in penalty for a return that reported no tax due at all. Interest and any owner-level filing obligations sit on top.

The penalty applies even when the partnership owes nothing, because Form 1065 is an information return. Filing on time is what protects you, not having a small or zero balance.

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04Do the Foreign Owners Have Their Own US Filings Too?

Often yes. If the partnership earns income effectively connected to a US trade or business, it generally must withhold US tax on the share allocated to each foreign owner and report it on Forms 8804 and 8805, and each foreign owner typically files a Form 1040-NR to reconcile it. If the company has no US-connected income, those obligations may not apply, but the partnership return itself still does. Which of these lands on you depends on what the business actually does and where its income comes from, which is exactly the part worth confirming with an advisor rather than guessing.

05What Should a Multi-Owner LLC Do Right Now?

1. 01Confirm how many owners the LLC had during the tax year. Two or more, and you are on the September 15 partnership track unless you elected corporation treatment.
2. 02Check whether an extension was filed in the spring. If it was, September 15 is your date. If it was not, the return is already overdue and the penalty is running.
3. 03Gather each owner's details and the year's income and expenses so the 1065 and every K-1 can be prepared accurately.
4. 04Have it filed. We prepare the partnership return, issue each owner their K-1, and handle any foreign-owner withholding so nothing on this list is left to chance.

06Can Prodezk Handle the Filing This Close to the Deadline?

Yes, and this is the point in the year to move. With the September 15 date roughly six weeks out, there is still room to prepare a partnership return properly rather than in a panic. We have handled US filings for founders across more than 190 countries for over two decades, and the multi-owner case is a routine one for us even when the single-owner guides skip it. Speak with an advisor and we will tell you exactly what your LLC owes and file it on time.