Form 1040-NR and the June 15 Deadline: The Personal US Tax Return Many Non-Resident LLC Owners Forget

If you own a US LLC as a non-resident, you probably already know about the company-level filings: Form 5472 with its pro forma Form 1120, due in April. What far fewer owners know is that there may be a second, personal filing — Form 1040-NR, the US Nonresident Alien Income Tax Return — and for most non-residents living abroad, its deadline is June 15. This year, that date falls on Monday, June 15, 2026. Miss it, and the consequences range from a 5 percent-per-month penalty to a little-known rule that can erase your deductions entirely.

Two Separate Filings, Two Separate Deadlines

A single-member LLC owned by a non-resident is a disregarded entity. The LLC itself files Form 5472 attached to a pro forma Form 1120 — that is an information filing about the company. But the LLC's income does not stop there: for US tax purposes, it flows directly to you, the owner, as if the company did not exist.

That is where Form 1040-NR comes in. It is your personal US tax return as a nonresident alien, and it is a completely separate obligation from the 5472. Filing one does not satisfy the other.

Who Actually Has to File Form 1040-NR

According to the IRS, you must file Form 1040-NR if, among other situations, you were a nonresident alien engaged in a trade or business in the United States during the year — and notably, this filing duty applies even in years where the activity produced little or no taxable income. You must also file if you had US-source income on which the tax owed was not fully covered by withholding at the source.

There is also a reason to file even when you are not required to: the IRS will only allow refunds of over-withheld tax, and deductions or credits against your US income, if you file a timely and accurate return. Owners of US rental property who elect to treat rental income as effectively connected income are a classic example — without a timely return, the deductions disappear.

Whether your LLC's activity makes you "engaged in a US trade or business" (ETBUS) depends on facts like dependent agents and US operations. Many non-resident owners who sell remotely into the US are not ETBUS and owe no US income tax — but the analysis is individual, and withholding, rental property, or US-based operations can change the answer.

Why June 15 and Not April 15

The IRS sets two different deadlines for Form 1040-NR. If you received wages as an employee subject to US income tax withholding, or you have an office or place of business in the United States, your deadline is the 15th day of the 4th month after year end — generally April 15. If neither applies — the typical case for a non-resident founder running an LLC from abroad — your deadline is the 15th day of the 6th month: June 15.

If You Need More Time: Form 4868

If you cannot file by June 15, you can request an automatic six-month extension by filing Form 4868 — but it must be submitted by your regular due date. For filers whose deadline is June 15, a timely Form 4868 extends the filing date to December 15.

One critical caveat: an extension of time to file is not an extension of time to pay. If you expect to owe US tax, the amount is still due with the original deadline, and interest accrues on anything unpaid after that date.

What Late Filing Actually Costs

The failure-to-file penalty is usually 5 percent of the unpaid tax for each month, or part of a month, the return is late — capped at 25 percent. A separate failure-to-pay penalty of 0.5 percent per month can apply on top, plus interest. If no tax is due, these percentage penalties have nothing to attach to — but that does not make late filing harmless, because of the rule below.

The 16-Month Rule: How Late Filers Lose Their Deductions

This is the trap that catches non-residents who assume filing late is a minor issue. To claim deductions and credits on Form 1040-NR, the return must be filed within 16 months of the due date. The IRS has the right to deny all deductions and credits on returns filed after that window.

The result can be brutal: income that is effectively connected with a US trade or business is normally taxed at graduated rates on the net amount after deductions. File too late, and the IRS can assess tax on your gross income — no expense deductions, no credits. A business that barely broke even can suddenly generate a real tax bill, simply because the return was filed more than 16 months late.

A Quick June Checklist for Non-Resident LLC Owners

First, confirm whether you were engaged in a US trade or business in 2025, or had US-source income that was not fully covered by withholding. Second, if a Form 1040-NR is required or beneficial, file it by June 15, 2026 — or submit Form 4868 by that date to extend to December 15. Third, if you expect to owe tax, pay your best estimate now, because the extension does not stop interest. And finally, never let a required return drift past the 16-month mark — that is where deductions die.

Have Questions About Your Own Situation?

Whether you actually need to file Form 1040-NR depends on your specific activity, structure, and income — and getting it right is much cheaper than fixing it later. If you would like to talk it through with the MP Partner experts team, we offer a free consultation: no pressure, no hard sell, just clear answers.

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