SB 543 Explained: California's 15-Day ADU Permit Rule in 2026

What Is SB 543?

SB 543 is a California law that slashes the mandatory permit review timeline for ADU applications from 60 days to 15 days. This is one of the most impactful ADU reforms in recent years — it forces cities to process conforming ADU applications quickly or face automatic approval.

Key Provisions of SB 543

• 15-day review window: Cities must approve or deny a conforming ADU application within 15 days of receiving a complete application.
• Deemed approved: If the city fails to act within the 15-day window, the application may be deemed approved by operation of law.
• Ministerial process: ADU permits remain ministerial (no discretionary review, no public hearing, no environmental review under CEQA).
• Complete application: The clock starts when the city receives a complete application — if they request corrections, the clock resets.

How to Take Advantage of SB 543

The 15-day timeline only works in your favor if your application is complete and conforming. Here's how to maximize your chances:

1. Submit a complete package: Site plan, floor plan, elevations, structural drawings, Title 24 energy calculations, and all required forms. Missing items give the city a reason to send a correction letter and reset the clock.
2. Use pre-approved plans: If your city offers them, pre-approved plans skip most of the review since they've already been vetted.
3. Meet objective standards: Setbacks, height, size, and all code requirements must be met. Any deviation gives the city grounds for denial.
4. Document your submission date: Keep a paper trail — email confirmations, counter receipts, timestamps. This matters if you need to assert deemed-approved status.

What If Your City Misses the Deadline?

If 15 days pass without action:

• Send a written notice to the planning/building department citing SB 543 and your submission date.
• Request written confirmation that your application is deemed approved.
• If the city disputes, consult with an attorney — HCD (Housing and Community Development) can also intervene.

SB 543 vs. Previous Timeline

For more on California ADU laws, see our 2026 law updates and legal requirements guide.