Harper Tax CPA
1) Federal (IRS) — Form 1120-S Extension & Key Dates
Federal filing due date (1120-S)
Form 1120-S is due the 15th day of the 3rd month after year-end. For calendar-year filers, that’s “mid-March.”
Calendar-year example (Tax year 2025 return filed in 2026):
- IRS 1120-S due: March 16, 2026 (March 15 falls on a Sunday)
Federal extension (Form 7004)
To extend the 1120-S filing deadline, file Form 7004 by the original due date. This is an automatic extension of time to file.
Critical rule: An extension is time to file, not time to pay.
Even though most S corps don’t owe federal income tax at the entity level, you can still have time-sensitive items (built-in gains tax in rare cases, payroll filings, state/local taxes, etc.) that are not extended by Form 7004.
2) Oregon (DOR) — OR-20-S Due Date, $150 Minimum Tax, and Extensions
Oregon S corporation return: OR-20-S
Oregon generally requires an S corporation doing business in Oregon or with Oregon-source income to file OR-20-S.
Oregon due date (OR-20-S)
Oregon corporate returns are due the 15th day of the month following the federal due date.
Calendar-year example (TY 2025):
- Federal due March 16, 2026 → Oregon due April 15, 2026
Oregon minimum excise tax (yes, even for S corps)
If your S corporation is doing business in Oregon, expect the $150 minimum excise tax at the entity level.
Oregon extension mechanics (key clarification)
Oregon’s extended due date is generally the 15th day of the month following the federal extended due date.
Translation: if you timely extend federally, Oregon’s extended due date typically lands one month after the federal extended deadline.
Important: Oregon follows the same principle as the IRS—extension to file ≠ extension to pay. Pay by the original due date to reduce late-payment penalties and interest.
Oregon estimated payments (tightened language)
Oregon corporate estimated tax payments are generally due April 15 / June 15 / September 15 / December 15 for calendar-year filers if you are required to pay estimates.
A common rule of thumb: estimates are generally required if you expect Oregon corporate tax to be $500 or more (including minimum tax). If you’re below that level, you’re often not required to make estimates—but confirm based on your facts.
3) Portland & Multnomah County — Business Tax Returns and Extensions
If your S corp is “doing business” in Portland, you’re commonly dealing with:
- City of Portland Business License Tax
- Multnomah County Business Income Tax
(often administered through the same local revenue system/process)
Portland/Multnomah filing due date (typical)
Local business tax returns are generally due the 15th day of the 4th month after year-end.
Calendar-year example: typically April 15 (unless a weekend/holiday shifts it).
Extension window
Portland generally allows a 6-month extension (commonly landing around October 15 for calendar-year filers).
The Portland rule that matters most
An extension of time to file is not an extension of time to pay.
If you extend, you should still pay your best estimate by the original due date to reduce late-payment exposure.
Practical Portland takeaway:
- Extend by the local due date (often April 15)
- Pay by the local due date (often April 15)
- File the extended return by the extended deadline (often October 15)
4) Metro Supportive Housing Services (SHS) Business Income Tax (if applicable)
If your business is in the Metro jurisdiction and meets filing requirements, Metro SHS introduces another income-tax-style filing.
Key principle remains the same:
- Pay by the original due date (extension typically doesn’t extend the payment deadline)
- Extension may be tied to making a timely extension payment and/or filing extension information, depending on the tax year’s instructions
Calendar note: Metro due dates can differ by tax year due to weekend/holiday alignment. Don’t hard-code “April 16” as a universal rule—treat it as tax-year-specific when you cite it.
5) TriMet Transit Payroll Tax — Quarterly Deadlines (Not an Income-Tax Extension Item)
TriMet is typically a payroll-side requirement, reported with quarterly payroll filings (Form OQ).
Form OQ quarterly due dates:
- Q1: April 30
- Q2: July 31
- Q3: October 31
- Q4: January 31
Critical separation: Extending your 1120-S or OR-20-S does nothing to extend payroll filings. You can be “perfectly extended” for income tax returns and still be late on Form OQ.
Portland S-Corp Deadline Cheat Sheet (Calendar-Year, Tax Year 2025 Example)
|
Item |
Typical Due Date |
Extension? |
Pay by Original Due Date? |
|
IRS Form 1120-S |
March 16, 2026 |
Form 7004 |
If anything owed |
|
Oregon OR-20-S |
April 15, 2026 |
Generally follows federal extension timing |
Yes |
|
Portland/Multnomah business taxes |
Typically April 15, 2026 |
Generally ~6 months (often to Oct 15) |
Yes |
|
TriMet payroll tax (Form OQ) |
Apr 30 / Jul 31 / Oct 31 / Jan 31 |
Not an income-tax extension item |
Yes—quarterly |
|
Metro SHS (if applicable) |
Varies by tax year |
Often extension available |
Yes |
Fast Checklist for a Portland S-Corp Extension (Calendar-Year)
- File IRS Form 7004 by March 16, 2026 (TY 2025 example).
- Plan for OR-20-S due April 15, 2026 and pay the $150 minimum tax by the original due date.
- If in Portland/Multnomah, extend by the local due date and pay your estimate by the local due date (commonly April 15).
- Do not miss payroll filings: calendar Form OQ due dates (Apr 30 / Jul 31 / Oct 31 / Jan 31).
- If Metro SHS applies, confirm the tax-year specific due date and payment rule.
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