A homeowner in Bozeman's Flanders Mill neighborhood built a 600-square-foot accessory dwelling unit for about $100,000. Rent from the unit now covers the payment and then some, a straightforward case for why an ADU pencils out in a market where a big share of listings still clear seven figures. That math depended on one assumption: no city could tack an impact fee onto the project. For two years, Montana law said exactly that.
If you're weighing the same move today, whether to house a parent, add rental income, or make a move-up purchase work financially, that assumption is no longer safe to make without a phone call first. Bozeman's own government website now says the opposite of what the statute says, and neither the city nor the state has cleared up which one governs your permit.
The Deal Homeowners Thought They Had
In 2023, Montana passed a package of housing bills nicknamed the "Montana Miracle," aimed at adding supply without forcing cities to build new roads and sewer lines for every unit. Senate Bill 528 required every residential lot in the state to allow at least one ADU by right, no discretionary hearing required. The same round of reforms wrote a companion protection into state law, the one that matters most for anyone budgeting a build: a municipality could not charge an ADU-specific impact fee, the one-time charge cities use to fund roads, water, and sewer capacity for new construction.
That prohibition is still written into state law today. Montana Code Annotated 76-2-345 lists what a local government may not do to an accessory dwelling unit, and one line states plainly that a municipality may not "assess impact fees on the construction of an accessory dwelling unit."
The reform wasn't left to chance, either. An advocacy group called Montanans Against Irresponsible Densification sued to block the broader 2023 package, arguing the state had stripped local zoning authority without justification. A Gallatin County district court initially agreed and issued an injunction. In 2024, the Montana Supreme Court overturned that ruling and upheld the reforms, including the Senate Bill 528 ADU mandate, finding that expanding housing supply was a legitimate state interest. This isn't some overlooked clause tucked into a late-session bill. It's part of a package that went all the way to the state's highest court and survived, with the impact fee ban still standing at MCA 76-2-345 as of this writing.
What Bozeman's Own Website Now Says
Here's the part that doesn't square. The City of Bozeman's Impact Fees page, the one homeowners and builders are directed to before pulling a permit, states that "due to recent legislation at the state level," ADUs "will be assessed impact fees beginning February 1st, 2026."
That date isn't hypothetical anymore. It's seven months behind us as of this writing, which means the city's position, whatever its legal basis, is currently in effect on new applications. The page doesn't cite a bill number. It doesn't explain how a city can charge a fee that the codified statute says it can't. It just states the new rule and moves on to fee schedule versions and inflation adjustments.
Here's the contradiction laid out plainly:
| What the 2023 reform put into state statute | What Bozeman's website currently states |
|---|---|
| Municipalities may not assess impact fees on ADU construction (MCA 76-2-345) | ADUs "will be assessed impact fees beginning February 1st, 2026" |
| Cities cannot require off-street parking for ADUs | 2025 legislation reinstated counties' authority to require ADU parking |
| Ban upheld by the Montana Supreme Court in 2024 | City page cites unnamed "recent legislation" with no bill number |
The 2025 Legislature Muddied It Further
Part of the confusion traces back to the 2025 legislative session, when lawmakers revisited the 2023 framework. Senate Bill 532 is the bill most closely tied to ADU rules that year, and coverage of it doesn't agree on what it actually did. The Sightline Institute's recap describes SB 532 as extending by-right ADU approval to parcels outside city limits, meaning unincorporated Gallatin County, while separately noting the 2025 session reinstated counties' ability to require parking for ADUs, a rollback from the 2023 ban on parking mandates. The Reason Foundation's analysis of the same session describes 2025 as the year Montana "expanded into other areas of housing policy, including impact fees," without specifying that ADU fees for cities were the target.
Neither source states that Bozeman, a city rather than a county, gained new authority to charge ADU impact fees. If that authority came from somewhere, it isn't showing up clearly in the public record of what passed. That's the actual takeaway for anyone budgeting a project right now: the paper trail doesn't currently connect the fee Bozeman is charging to a specific, named change in state law. You're not going to resolve that by reading a blog post, including this one. You resolve it by asking the city directly and getting the citation in writing.
What This Actually Costs If It's Real
Assume for a moment the fee holds. ADU-specific impact fees in states that allow them typically run $10,000 to $30,000 per unit, a range worth knowing even though Bozeman hasn't published its specific ADU fee schedule. Layer that onto existing Bozeman-area construction costs, where a basic modular or prefab unit can come in under $100,000 but a custom attached ADU built with local labor and materials commonly runs $150,000 to $250,000 or more, and the fee stops being a rounding error. It's the difference between a project that pays for itself in a few years of rent and one that takes considerably longer.
Context matters here too. Bozeman's median single-family sale price was $715,000 in February 2026, down from a peak of $898,000 in May 2023, according to Montana Free Press. The market has cooled, but nearly 40% of single-family homes in the city were still selling above $1 million even as prices softened. An ADU is one of the few tools that lets a household offset a purchase at that price point with rental income or a place for extended family, which is exactly why the fee question isn't cosmetic. It changes whether the numbers work.
The One Discount That Might Offset It
Bozeman does run a program that could soften the blow, but it's narrower than it sounds. The Downtown Residential Incentive Grant reimburses up to 50% of residential-related impact fees, capped at $50,000 per project, for qualifying studio and one-bedroom units built within Bozeman's Downtown Urban Renewal District. If your ADU project happens to sit inside that specific district boundary, this grant is worth applying for. If you're building a backyard cottage in a newer subdivision outside downtown, which describes most detached ADUs in Bozeman, this program almost certainly doesn't apply to you.
Before You Pull a Permit
Given the gap between what the statute says and what the city is charging, treat the following as a checklist for your first call to Bozeman's Community Development department, not optional background reading:
- Ask whether your specific parcel is currently assessed a residential impact fee for an ADU, and get the dollar figure in writing for your unit's size and type.
- Ask the city to name the specific state legislation it's relying on for the February 2026 change, and read the bill text yourself rather than taking the citation secondhand.
- Confirm whether your project falls inside the Downtown Urban Renewal District boundary and, if so, apply for the Downtown Residential Incentive Grant before you pay any impact fee in full.
- If your build is in unincorporated Gallatin County rather than inside Bozeman city limits, ask which rules apply. SB 532's provisions were aimed at county parcels, not city ones, so your fee exposure may look different entirely.
- Get the fee determination date confirmed. Bozeman ties the applicable fee schedule to the date your permit passes prescreen review, not the date you submit, so timing your application matters.
Frequently Asked Questions
Does the new fee apply to ADUs that were already built before February 2026? Bozeman's own rules tie the applicable fee to the date a project passes prescreen review, so an ADU that cleared that step before February 1, 2026 should fall under the prior schedule. Confirm this directly with the city rather than assuming it, given how unsettled the broader policy is right now.
Is the fee the same inside Bozeman city limits and in unincorporated Gallatin County? Likely not. The city's posted change applies within Bozeman. The 2025 legislative changes tracked by Sightline and Reason were aimed specifically at ADUs outside city limits, which suggests county parcels may be operating under a different set of rules entirely.
Could this raise the value of ADUs that already exist? It's a reasonable question to ask your agent, though not one the public record answers directly. If building a new ADU now costs more than it did in 2025, an existing income-producing ADU on a property you're considering could carry more of the value than it would have a year ago. That's a case to make property by property, not a rule to assume.
The policy landscape here is moving faster than most sources have caught up with, which is exactly why a five-minute call before you commit to a builder or a purchase price beats relying on any single write-up, including this one. If you're weighing a Bozeman property with ADU potential, or trying to figure out what a build actually pencils out to at today's fee structure, Cameron Hahn can help you get a straight answer before you sign anything.
