HOW A MILLS ACT ASSESSMENT IS ACTUALLY CALCULATED ON AN LA LOFT

Most explanations of the Mills Act stop at "it lowers your property taxes." That is true often enough to be useful and vague enough to be dangerous, because the Mills Act does not apply a discount to your existing bill. It replaces the entire basis on which the property is valued. Understanding which basis you are on is the difference between a saving you can count on and a surprise.

The three values every California property has

Under Proposition 13, your assessment is normally a factored base year value: what you paid when you bought, adjusted upward by no more than 2% a year. That is why two identical lofts on the same floor can have very different tax bills — one owner bought in 2009, the other in 2024.

A Mills Act property is assessed a third way. Under Revenue and Taxation Code sections 439–439.4, the county values it by the income capitalization approach: it estimates what the property would earn as an income stream, then divides that by a capitalization rate. The California Office of Historic Preservation describes the mechanics directly — annual income divided by a capitalization rate, with residential properties using comparable local rents and commercial properties using actual rental receipts.

The Assessor then compares the restricted value against the other applicable values and enrols the lowest. That last step is the one people miss, and it is where most of the confusion about Mills Act savings comes from.

Why the saving is large for some lofts and near zero for others

Work through what the income approach is sensitive to and the pattern becomes obvious.

The numerator is the rent the unit could command. The denominator is a capitalization rate built from several components set by statute rather than negotiated. Because the rate sits in the denominator, a higher rate produces a lower assessed value and a larger saving.

Now consider two buyers in the same DTLA building:

• Buyer A bought a loft in 2007 and has held it since. Her Prop 13 factored base year value is far below today's market. A Mills Act restricted value calculated from current rents may well come out higher than the value she is already enrolled at. The Assessor enrols the lower figure, so her bill does not change much — and she has taken on maintenance obligations and a recorded contract for very little tax benefit.
• Buyer B is buying that same floorplan today. His base year value resets to the purchase price. The restricted value, driven by achievable rent rather than sale price, is likely to land well below it. The saving is real and can be substantial.

This is the single most useful thing to understand about the Mills Act in a loft market: the benefit is generally largest for recent buyers at current prices, and smallest for long-term owners. It is a new-purchase incentive far more than a legacy-owner one. That is also why a Mills Act contract on a building is a stronger selling point to a buyer than it ever was to the seller.

Rent drives the number, not the sale price

Because the numerator is rental income, the things that move a Mills Act assessment are the things that move rent: unit size, layout, parking, light, outdoor space, building amenities, and the rents actually being achieved nearby.

That produces a result buyers find counter-intuitive. A dramatic top-floor loft with soaring ceilings might sell at a significant premium over a plain unit two floors down, and yet not rent for a proportionate premium. Where sale price outruns rent, the gap between the Prop 13 value and the restricted value widens, and the Mills Act saving grows. The features that command a purchase premium and the features that command a rent premium are not the same features, and only the second set drives this calculation.

What the contract costs you, in cash and in freedom

The tax treatment is one side of a bargain. The other side:

• A recorded contract, minimum ten years, evergreen. It extends automatically by a year at a time and transfers to the next owner on sale, binding them to the same terms.
• Restoration and maintenance obligations. The contract commits you to a standard of care, often with a schedule of work attached.
• Periodic inspections. Compliance inspections are required every five years. Los Angeles City Planning's draft policy updates propose collecting fees specifically to fund them, along with fees for non-compliance and stronger enforcement provisions — including pursuing cancellation where an owner is unresponsive after six months of attempted contact.
• Limits on what you may change. This is the one that bites in a loft. Windows, facades and other character-defining features are usually exactly what the contract protects, and they are exactly what owners most often want to replace.

Running the numbers before you write an offer

A defensible estimate takes four inputs, and none of them come from a listing description:

1. The recorded contract. Its date, its terms, and the obligations that pass to you.
2. The current restricted assessed value from the County Assessor. The actual enrolled figure, not a projection.
3. Achievable rent for that specific unit type — which is what the valuation is built from.
4. What your own base year value would be at your purchase price — because the comparison between the two is the saving.

Then compare the two figures rather than accepting a headline number. A seller quoting last year's tax bill is quoting a figure produced under the previous owner's circumstances, and the useful question is not what they paid but what you would pay.

One thing worth knowing before you start: in the City of Los Angeles the program is not currently accepting new applications, so this analysis applies to buildings that already hold a contract. For the due-diligence checklist that goes alongside it, see what to verify before counting the tax savings.

Sources

• California Office of Historic Preservation, Mills Act Program — Government Code 50280–50290, Revenue and Taxation Code 439–439.4, the income capitalization approach and contract terms.
• Los Angeles City Planning, Mills Act Program Draft Policy Updates FAQ — five-year compliance inspections, proposed fees and enforcement provisions.

General information only, not tax or legal advice. Capitalization-rate components and assessment practice are set by statute and administered by the County Assessor; confirm any figure with the Assessor and a qualified tax professional before relying on it.