The Lease Addendum for Purpose of Future Costa-Hawkins Rent Increase & When You Should You Use It

What Is the Lease Addendum for Purpose of Future Costa-Hawkins Rent Increase—

And When Should You Use It? 

Berkeley rental housing providers who own fully-covered, rent-controlled units should take note of an important tool available on our [Forms page]: the Lease Addendum for Purpose of Future Costa-Hawkins Rent Increase. This form is used when approving a replacement tenant or subtenant in a rent-controlled unit and is essential for preserving your legal right to reset the rent and lease terms when the last original tenant moves out.

Why This Addendum Exists

Under California’s Costa-Hawkins Rental Housing Act, rental housing providers may increase the rent to market and establish a new lease with new and different terms after all original occupants of a rent-controlled unit have permanently vacated. However, if you accept rent from a new occupant (such as a replacement roommate or subtenant) without formally documenting their status—and without giving timely notice of a new rent—you may forfeit your right to a Costa-Hawkins increase.

That’s where this addendum comes in.

What the Addendum Does

This form documents the following:

• The new occupant is not an original tenant as defined by California Civil Code § 1954.53 and Berkeley Rent Board Regulation 1013;

• The landlord may lawfully raise the rent and offer a new lease agreement with different terms once the last original tenant permanently vacates;

• The acceptance of rent from the new occupant does not waive the landlord’s right to a Costa-Hawkins rent increase, as long as the legal steps are followed.

Why This Matters: Not Just a Rent Increase—A New Lease, Too

Under both California state law and Berkeley Rent Board Regulation 1013, once all original tenants have permanently vacated a rent-controlled unit, the landlord has the right to:

• Raise the rent to market and

• Offer an entirely new lease with updated terms and conditions.

This is more than a simple rent increase—it’s a legal opportunity to reset the terms of tenancy. That might include a new lease duration, house rules, or other policy changes.

⚠️ Caution: If you accept rent from the remaining non-original occupant after the last original tenant moves out—without first serving notice of a new rent and lease—you may accidentally lock yourself into a continuing tenancy under the old rent and terms.

That’s why having this signed addendum before the original tenant leaves is so important.

When to Use It

Use this form when:

• You are approving a replacement tenant or subtenant in a rent-controlled (fully-covered) unit; and

• That person did not sign the original lease, and

• They did not move in within 30 days of the original tenancy start date.

When Not to Use It

• Do not use it for exempt units (such as single-family homes, condos, or newly built properties not subject to full rent control).

• Do not use it when entering into a brand-new tenancy with entirely new tenants—you’ll already be setting market rent and new lease terms at that point.

• Do not rely on this form to justify a rent increase if you've already accepted rent from a subtenant after the last original tenant moved out and before serving a proper notice of new rent and lease terms.

📄 Need the form?
You’ll find it in our Rental Housing Forms Library in the Lease Modifications section under Costa-Hawkins Addendum.

Make sure to keep a signed copy with your lease documents to protect your rights.

📚 Legal References

• California Civil Code § 1954.53(d)
  Governs rent increases under the Costa-Hawkins Rental Housing Act, including the landlord’s right to set initial rent and offer a new lease once all original occupants have vacated.
  Read the full text on the California Legislative Information website.

• Berkeley Rent Board Regulation 1013
  Defines “original occupant” and clarifies the conditions under which a landlord may impose a vacancy rent increase and require a new rental agreement.
  View the full text of Regulation 1013.

Copyright © 2025 Berkeley Property Owners Association (BPOA). This document is for educational purposes only and does not constitute legal advice.