Is Your Rental Unit Legal? How to Check Before Your Tenant Does

Last week I inspected a unit where the tenant had already done her homework. Before she even called me, she had searched public databases and discovered something troubling: her unit’s address didn’t exist in the city’s official records.

She was right. The address wasn’t in ZIMAS. The Assessor showed fewer units than actually existed on the property. The building wasn’t in the LAHD rent registry despite being subject to rent stabilization.

She figured all of this out in about 30 minutes using free, public tools.

Could your tenant do the same thing? More importantly: do you know what they would find?

Why You Need to Check

Every piece of information I’m about to show you how to find is publicly available. Your tenants can access it. Their attorneys can access it. AI tools can help them interpret it.

If there’s a discrepancy between what the city thinks you have and what you’re actually renting out, you need to know about it before someone else discovers it.

What’s at Stake

• Habitability claims: An unrecognized unit may not meet habitability standards—and you can’t get a Certificate of Occupancy for a unit that doesn’t officially exist
• Rent collection: Courts have ruled that landlords can’t collect rent on illegal units in some circumstances
• Insurance: Your policy may not cover an unpermitted or unrecognized unit
• Liability: If someone is injured in an unrecognized unit, your exposure increases significantly
• Sale complications: Unpermitted units create major problems during due diligence
• Code enforcement: If the city discovers an illegal unit, they can require you to remove it or bring it to code

The good news: you can run the same searches your tenant can. Here’s how.

Step 1: Check ZIMAS (City of LA Properties)

ZIMAS (Zone Information and Map Access System) is the City of Los Angeles’s official parcel information database. It shows what addresses are officially associated with each property.

Go to ZIMAS →

How to Search ZIMAS

1. Go to zimas.lacity.org
2. Enter your property address in the search bar
3. Click on your parcel when it appears on the map
4. Look at the “Address(es)” section in the left panel
5. Note ALL addresses listed for your parcel

What to Look For

Does your rental unit’s address appear?

If you’re renting a unit at 1234½ Main Street, that exact address should appear in ZIMAS. Not just 1234 Main Street—but 1234½ specifically.

🚩Red Flag: Your unit’s address doesn’t appear in ZIMAS at all. This suggests the unit may not be officially recognized by the city as a legal dwelling.

Understanding Address Formats

LA uses various formats for multi-unit properties:

• Fractional addresses: 1234½, 1234¼, 1234¾
• Letter suffixes: 1234A, 1234B
• Unit numbers: 1234 #1, 1234 #2
• Rear designations: 1234 Rear, 1234R

Each legally established unit should have its own address entry in ZIMAS. If your property has 4 rental units but ZIMAS only shows 2 addresses, that’s a significant discrepancy.

Other ZIMAS Information

While you’re there, also note:

• Zoning: What’s the property zoned for? Does it allow the number of units you have?
• General Plan Land Use: Residential? Commercial? Mixed?
• Specific Plan Area: Some areas have additional restrictions
• Historic status: Historic properties have additional requirements

ZIMAS Only Covers City of LA

ZIMAS is for properties within the City of Los Angeles. If your property is in unincorporated LA County or another city (Pasadena, Glendale, Long Beach, etc.), you’ll need to check that jurisdiction’s parcel database instead.

Step 2: Check LA County Assessor

The LA County Assessor’s office maintains records of all properties for tax purposes—including how many units are on each parcel.

Go to LA County Assessor →

How to Search the Assessor

1. Go to portal.assessor.lacounty.gov
2. Click “Property Search”
3. Enter your address or APN (Assessor Parcel Number)
4. Find your property in the results
5. Look for “Units” or “Number of Units” in the property details

What to Look For

Does the unit count match reality?

Count the actual rental units on your property. Include the main house if it’s rented, any secondary units, ADUs, garage conversions, basement apartments—everything that functions as a separate dwelling.

Now compare to what the Assessor shows.

🚩Red Flag: The Assessor shows 2 units, but you have 3 (or 4, or 5) actual dwellings. The extra units may be unpermitted.

Why This Matters

The Assessor’s unit count reflects what’s been officially established through permits and inspections. If you have more units than the Assessor shows, it usually means:

• Someone converted space into a dwelling without permits
• An ADU was built without going through the proper process
• A garage or basement was converted illegally
• The property was subdivided without approval

Any of these creates legal exposure for you as the landlord.

Step 3: Check LAHD Rent Registry (RSO Properties)

If your property is subject to the Los Angeles Rent Stabilization Ordinance (RSO), it should be registered with the LA Housing Department.

Check RSO Status →

How to Check RSO Status

1. First, check if your property is subject to RSO using ZIMAS (look for “Rent Stabilization Ordinance” under Housing)
2. If it is RSO, go to housing.lacity.gov
3. Search the rent registry for your property
4. Verify your property appears and the unit count is correct

What to Look For

Is your RSO property registered?

If ZIMAS shows your property is subject to RSO, it should appear in the LAHD rent registry with the correct number of units.

🚩Red Flag: Your property is subject to RSO but doesn’t appear in the rent registry, or the registered unit count doesn’t match what you’re actually renting.

RSO Registration Requirements

RSO landlords must:

• Register all rental units with LAHD
• Pay annual registration fees
• Follow rent increase limits
• Comply with just-cause eviction requirements

Non-registration doesn’t exempt you from RSO—it just adds non-compliance to your list of problems.

Step 4: Check LADBS Permit History

The LA Department of Building and Safety maintains records of all building permits. This tells you what work has been officially approved.Check LADBS Permits →

How to Search Permit History

1. Go to ladbs.org and find the permit search
2. Enter your property address
3. Review all permits on file
4. Look for permits related to: unit additions, ADUs, conversions, electrical work, plumbing work

What to Look For

Does the permit history explain what exists?

If your property has an ADU, there should be permits for it. If the electrical panel was relocated, there should be a permit. If a garage was converted to living space, there should be permits for the conversion.

🚩Red Flag: Major work exists (additional units, relocated systems, converted spaces) but there are no corresponding permits on file.

Common Unpermitted Work

• Garage conversions to living space
• Basement apartments
• Backyard ADUs or “granny flats”
• Room additions
• Electrical panel upgrades or relocations
• Bathroom additions
• Kitchen additions in non-kitchen spaces

Red Flags and What They Mean

Here’s a summary of warning signs and their implications:

Unit Address Doesn’t Exist in ZIMAS

What it means: The city doesn’t recognize this address as a legal dwelling. The unit may have been created without permits or approval.

Risk level: High. This is the clearest indicator of an illegal unit.

More Units Than Assessor Shows

What it means: Additional dwellings were created without going through the permit process that would update Assessor records.

Risk level: High. Unpermitted units create liability, insurance, and legal exposure.

RSO Property Not in Rent Registry

What it means: You’re not complying with registration requirements. While this doesn’t affect unit legality, it indicates non-compliance and strengthens tenant claims.

Risk level: Medium. Easy to fix, but creates problems if discovered during a dispute.

No Permits for Visible Work

What it means: Work was done without city approval. May or may not meet code. Creates uncertainty about safety and compliance.

Risk level: Medium to High, depending on the work. Electrical and structural work without permits is more serious than cosmetic changes.

What to Do If You Find Problems

If Your Unit May Be Unpermitted

Don’t panic, but don’t ignore it either. Your options include:

1. Consult a permit expediter or architect

They can assess what exists, what would be required to legalize it, and whether legalization is feasible. Some unpermitted units can be brought into compliance; others cannot.

2. Understand the ADU amnesty programs

LA has programs that make it easier to legalize existing unpermitted ADUs. The requirements are less stringent than new construction. This may be a path forward.

3. Consult an attorney

If you have tenants in potentially illegal units, you need legal advice about your obligations, disclosure requirements, and options.

4. Get a professional assessment

Before making decisions, understand what conditions actually exist. A professional inspection can document the current state and identify what would need to change for compliance.

If You’re Not Registered with LAHD

This is fixable. Register your property, pay the fees, and get into compliance. The longer you wait, the more back fees you may owe.

If You Have Unpermitted Work

Depending on the work, you may be able to get retroactive permits (“permits to legalize”). This involves inspection and may require bringing work up to current code. Consult with LADBS or a permit expediter about your specific situation.

A Real Example

I recently inspected a property where my research revealed:

• The tenant’s address (with a ¼ designation) didn’t appear in ZIMAS at all
• The Assessor showed 2 units; I observed 3 distinct dwellings
• The property was subject to RSO but wasn’t in the rent registry
• No permits on file for the apparent conversion of the rear building into a duplex
• Active construction on another unit—also with no permits

The tenant had figured most of this out before she even called me. She used AI to help her research and interpret what she found. By the time I arrived, she already knew her unit probably wasn’t legal.

The landlord, when confronted with an inspection, responded badly—threatening me and demanding I leave. That response is now documented in my report, along with all the physical conditions I observed.

The tenant now has professional documentation of both the conditions and the landlord’s behavior. She has an attorney. She’s filing complaints with LAHD.

All of this was discoverable in public records. The landlord could have found it first.

The Bottom Line

The information is available. Your tenants can find it. AI tools make it easier than ever to search, cross-reference, and understand what the records show.

You can either discover problems proactively and address them on your terms, or wait for someone else to discover them and lose control of the situation.

Run the searches. Know what you own. And if you find discrepancies, deal with them before they deal with you.