Harper Tax CPA
Los Angeles S-Corporation Extensions & Payments (1120-S + CA 100S) — Plus the LA Business Tax Renewal (1000A)
If your S corporation operates in Los Angeles, you’re usually managing three separate compliance calendars:
- Federal S-corp return: IRS Form 1120-S
- California S-corp return: FTB Form 100S
- City of Los Angeles business tax renewal: Business Tax Renewal Form 1000A (LA Office of Finance)
The biggest trap: extensions extend filing, not payment—and LA’s renewal cycle is separate from IRS/FTB deadlines.
1) Federal: IRS Form 1120-S — due date, extension, and what “extension” really means
Federal due date (calendar-year S-corp)
Form 1120-S is due the 15th day of the 3rd month after year-end. For a calendar-year S-corp, that’s typically March 15, moved to the next business day if it falls on a weekend/holiday.
2025 calendar-year example: Monday, March 16, 2026 (since March 15, 2026 is Sunday).
Federal extension (Form 7004)
If you need more time to file 1120-S, file Form 7004 by the original due date to get an automatic filing extension.
Payment reality (important nuance)
Most S-corps have no federal entity-level income tax, but if yours does (for certain specialized situations), interest can still run if you don’t pay timely—so treat the original due date as your payment deadline if entity-level tax is in play.
2) California: FTB Form 100S — automatic extension, but payment is still due
California generally gives S-corps an automatic extension to file, but not an extension to pay.
CA 100S due date + extended due date
- Return due date: 15th day of the 3rd month after year-end
- Extended due date: 15th day of the 9th month after year-end
- Payment date: total tax owed is due on the original return due date
Weekend/holiday rule (fixes the common “March 15” confusion)
California extends the deadline to file and pay without penalty to the next business day when the due date falls on a weekend/holiday.
2025 calendar-year example: Original due date falls on Sunday, so the CA 100S file + pay deadline becomes Monday, March 16, 2026.
Do you file a California extension form?
Usually no—the extension is generally automatic. But if you’re making an extension payment, you may use the appropriate payment voucher/electronic payment process (commonly referenced as paying with the extension).
3) Los Angeles: Business Tax Renewal (Form 1000A) — separate calendar from income tax returns
LA’s business tax renewal is administered by the City of Los Angeles Office of Finance and follows its own annual renewal cycle.
LA renewal timing (the key takeaway)
- Business taxes are due January 1
- They become delinquent if not paid by the last day of February
- For 2026 renewals, the City states March 2, 2026 is the last day for timely filing (because of calendar timing)
This is why an S-corp can be extended federally/California and still need to complete the LA renewal earlier.
Calendar-Year Los Angeles S-Corp Cheat Sheet (2025 year / 2026 deadlines)
|
Item |
What’s due |
Due date rule |
2026 date example (for 2025 year) |
|
IRS Form 1120-S |
File or extend (7004) |
15th day of 3rd month after year-end (next business day if weekend/holiday) |
Mar 16, 2026 |
|
CA Form 100S |
File (extension available) |
15th day of 3rd month (next business day if weekend/holiday) |
Mar 16, 2026 |
|
CA S-corp payment |
Pay total CA tax owed |
Due on original CA return due date |
Mar 16, 2026 |
|
LA Business Tax Renewal (1000A) |
Renew/pay timely |
Due Jan 1; delinquent after last day of Feb (city rule) |
Timely by Mar 2, 2026 |
Practical workflow (recommended) so nothing gets missed
Step 1 — Put LA renewal on a separate calendar
Treat LA’s renewal as its own compliance cycle. Don’t let IRS/FTB extension timing distract you from the city deadline.
Step 2 — Decide: file vs extend (IRS + CA)
- If you can’t finish 1120-S, file 7004 by the due date.
- Plan to file CA 100S by the extended due date if you need time—but still pay by the original due date.
Step 3 — Handle payments by the original deadlines
- Federal: usually no entity-level tax, but if there is, treat the original deadline as the payment deadline.
- California: payment is due by the original CA deadline (even if filing is extended).
- LA: renewal is due on the city’s cycle (timely by Mar 2, 2026 for 2026 renewals).
FAQs (Los Angeles S-Corp Edition)
Does IRS Form 7004 extend California Form 100S?
No. California has its own extension rules/timing for Form 100S.
If I extend CA 100S, do I still pay by the original due date?
Yes—California’s extension is an extension to file, not an extension to pay.
Is the LA Business Tax Renewal part of my 1120-S or CA 100S?
No. It’s a City of LA Office of Finance renewal with its own deadline and delinquency rules.
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