Key takeaways
- An S corporation with Alaska nexus files Form 6000, page 1 only, with the S Corporation box checked and federal Form 1120-S pages 1 through 5 attached.
- By the 2024 instructions' rule, a calendar-year 2026 return is due April 15, 2027, or October 15, 2027 on extension (derived).
- Alaska tax can still apply to built-in gains and excess net passive income, at a rate of 9.4% in the 2024 instructions.
- Telework employees, leased property and sales into Alaska can each create nexus; a Commerce registration alone does not.
What Alaska requires from an S corporation
The Department of Revenue instructions for Form 6000 say an S corporation doing business in Alaska must file an Alaska return, although Alaska does not tax the corporation on pass-through items of income. Generally the filing requirement is met by Form 6000, page 1 only, with the S Corporation box checked.
Leave Schedule A and the other pages blank unless a corporate-level tax applies. Attach a copy of pages 1 through 5 of the federal Form 1120-S. The instructions say an LLC characterized as a corporation for federal income tax purposes follows the corporation instructions. They do not name S elections in that sentence, so for an LLC that elected S status, treat it as a corporation return and confirm in the 2026 instructions.
The instructions I read describe no election for entity-level tax on behalf of shareholders, no composite return and no nonresident shareholder withholding for S corporations. That is not a statement about all Alaska law, so for clients with nonresident owners, note in the engagement letter that you reviewed only the Form 6000 instructions.
Decide whether the client has Alaska nexus
The instructions say every corporation with nexus must file. Listed nexus activities are owning or using property in the state, including leased or mobile property, having employees present in the state including telework, making sales into the state, and generating income from sources within the state. Registering with the Department of Commerce does not by itself create a filing requirement.
Take a Washington S corporation with one bookkeeper working remotely from Anchorage. Telework is on the list, so the working conclusion is nexus and a Form 6000, page 1 filing. Whether any tax is owed is a separate question, and for a client with no built-in gains or passive income it will usually be nothing, which you confirm from the federal return rather than assume.
The instructions do not address a corporation whose only Alaska tie is one shareholder's residence; that ownership is not on the nexus list, which describes corporate activity. If the answer rests on judgment, write the reasoning in the workpapers.
Due dates and extensions for tax year 2026
The 2024 instructions give the S corporation return due date as the 15th day of the fourth month after year end and the extended due date as the 15th day of the tenth month, for all tax years. Applied to a calendar-year 2026 S corporation, that is April 15, 2027 and October 15, 2027.
A federal extension automatically extends the Alaska filing due date. The filer still has to check the extension box on Form 6000, page 1, and for an e-filed return attach a pdf of Form 7004. The IRS describes Form 7004 as an automatic 6-month extension that generally must be filed by the regular due date.
Payment does not move. The instructions put the S corporation payment date at the 15th of the third month for all year-ends, which is March 15, 2027 for a calendar-year 2026 return, and say an extension of time to file is not an extension of time to pay. A built-in gains client that owes tax therefore pays in March even if the return goes on extension.
The federal Form 1120-S date for a calendar-year 2026 corporation follows the general rule of the 15th day of the third month, March 15, 2027, which I derived from the rule and did not read in 2026 instructions. The 2025 return was due March 16, 2026 because March 15 fell on a Sunday.
When Alaska tax can still apply
The 2024 instructions say Alaska imposes both the federal excess net passive income tax and the corporate-level tax on built-in gains, calculated at the highest Alaska marginal rate of 9.4%. If either applies, complete the Alaska schedules, attach the federal schedules that compute the tax, and enter the corporate-level tax on Form 6000, Schedule E, line 6. The instructions I read give no worked computation.
Built-in gains matter for a client that converted from a C corporation and sells appreciated assets inside the recognition period. Ask for the date of the Form 2553 election, the prior C corporation balance sheet, and the asset appraisal at conversion. Without those, neither the federal nor the Alaska computation can be done.
Excess net passive income applies to an S corporation with accumulated earnings and profits from C years and passive investment income. A client with rental income, interest and no active operations is the case to check before assuming the page 1 filing is enough.
E-file, signature and penalties
A taxpayer must electronically file any return unless the Department grants a waiver. The stated penalty for not e-filing is the greater of $25 or 1% of the tax due, so on a return showing tax, 1% of the tax applies once it exceeds $25. The instructions do not say how this works on a zero-tax return, so ask the Department. A waiver is requested on Form 773 at least 30 days before the due date.
The instructions I read do not say Form 6000 must be transmitted only with the federal return; they list Revenue Online at online-tax.alaska.gov. Confirm which path your software supports and keep the acknowledgment.
An authorized officer must sign. If the corporation wants the Department to discuss the return with you, check the paid preparer authorization box in the signature area; it covers the signing preparer only, and revoking it takes Form 774.
For a late return the failure to file penalty is 5% of the unpaid tax for each 30-day period or portion, up to a maximum of 25% of the unpaid tax. If a client owes $40,000 of built-in gains tax and files two months and ten days late, that is three periods, 15%, and a $6,000 penalty. The 25% cap does not bite until the sixth period. The late payment penalty uses the same 5% and 25% figures, but where both apply only the failure to file penalty is imposed. I did not verify the interest rate on late Alaska payments.
Federally, the 2025 instructions state a late-filing penalty of $255 per shareholder for each month or part of a month, up to 12 months. That applies to the 2025 return due in 2026; the 2026 amount is unconfirmed, so check before quoting $255 for 2026.
The biennial report is a different filing
The Division of Corporations at Commerce handles the biennial report, not the Tax Division. A for-profit corporation created in an even-numbered year reports by January 2 of every even-numbered year, and one created in an odd-numbered year reports by January 2 of every odd-numbered year. Reports postmarked after February 1 incur a late fee.
Commerce says failure to meet its requirements could result in involuntary dissolution or revocation of authority to transact business. It runs on its own calendar, separate from Form 6000.
Documents to collect for the Alaska return
Most of the return comes from the federal file, so the Alaska-specific requests are short: a written answer on each nexus item above with the Alaska address of any employee, the lease or title for Alaska property, the Form 2553 acceptance letter, and the shareholder list that matches the Schedule K-1 data.
Wording to send: "For 2026, tell us whether any employee, contractor or inventory was physically in Alaska at any point, and attach the lease or payroll record if so. If none, reply 'none' and give us the name of whoever confirmed it." That reply, with its date, is your proof of the nexus conclusion; a blank is not.
In Usual, a file request item can be marked Not applicable, which records the client's answer against the engagement.