Impact fees are one-time charges local governments impose on new development to pay for the roads, water and sewer capacity, parks, schools, and emergency facilities that growth requires. Understanding how impact fees work means understanding three things at once: what the money can be spent on, how the amount owed is calculated, and what legal limits keep the charge from becoming something else. The fee is assessed on the developer, most often when a building permit is issued, and the revenue is locked to capital improvements that serve the new project. Existing residents are not supposed to pay for the infrastructure the newcomers will use, and the newcomers are not supposed to pay for problems that existed before they arrived.
Fee or Tax
The line between an impact fee and a tax is not cosmetic. A tax raises general revenue that a government can spend on almost anything. An impact fee is a regulatory charge tied to a specific burden a development places on public infrastructure, and the money can only be spent on capital improvements that serve that development.1Federal Highway Administration. Development Impact Fees / Mobility Fees Break that connection and courts will treat the charge as an illegal tax.
The authority to impose fees flows from state police power, delegated down to counties and cities. More than half the states have enacted specific enabling legislation that spells out what infrastructure qualifies and how the fee must be calculated. Where no such statute exists, local governments lean on general home-rule authority, which gives them less legal cover if a fee is challenged.
What Impact Fees Can Pay For
Impact fees fund capital improvements, not operations. The typical categories are transportation (new lanes, intersections, signals), water and sewer expansion, parks and recreation, fire and emergency stations, libraries, and schools. Money can go toward off-site regional infrastructure that serves the development, not only improvements at the project’s edge.2Federal Highway Administration. Development Impact Fees
Within those categories, eligible costs include land acquisition, design and engineering, construction, and the professional services needed to deliver an approved project. What the fees cannot cover: salaries for utility workers, road crews, or administrative staff, and debt service on bonds issued for infrastructure that predates the new development.
How the Fee Amount Is Calculated
Every defensible impact fee starts with a formal technical study, sometimes called a capital facilities plan or impact fee study. The study quantifies how much new infrastructure projected growth will require, what it will cost, and how those costs should be distributed across new projects. Without that document, the fee schedule has no legal foundation.
The Two Methods
Most jurisdictions use one of two approaches. The inductive method identifies a model facility (a fire station, a road lane-mile, a sewer trunk line), determines its cost and capacity, and uses those figures to calculate what each new unit of development should pay toward the next facility the system will need. It works when facilities of a given type are roughly interchangeable.1Federal Highway Administration. Development Impact Fees / Mobility Fees
The deductive method is more tailored. It begins with the jurisdiction’s master plan and growth projections, identifies the specific capital projects needed to serve that growth, prices each one, and distributes those costs across undeveloped property. Because it prices actual planned projects rather than generic facilities, the fees track local geography and system conditions more precisely.1Federal Highway Administration. Development Impact Fees / Mobility Fees
Service Units
Either method needs a standardized way to measure how much demand a project places on a system. That measurement is called a service unit. For transportation fees, the service unit is usually average daily vehicle trips generated by a land use. A single-family home might produce about 9 to 10 daily trips. A warehouse generates far fewer per thousand square feet; a fast-food restaurant generates dramatically more.
For water and sewer, the service unit is often a meter equivalency, where one single-family connection equals 1.0 and larger meters scale up in proportion to the capacity they draw.
The per-unit fee is the net eligible capital cost divided by the projected new service units. If a jurisdiction needs $10 million in new road capacity and expects 5,000 new equivalent dwelling units, the transportation fee is $2,000 per unit. A builder putting up 100 single-family homes pays $200,000 in transportation fees alone, and the same builder may owe separate fees for water, sewer, parks, and other categories.
What the Study Cannot Include
A hard legal constraint prohibits charging new development for existing infrastructure deficiencies. If a road is already failing before new homes are built, the cost of fixing it cannot be rolled into impact fees. The calculation must isolate the cost of new capacity that serves future growth. State statutes commonly bar using fee revenue for general upgrades, routine maintenance, operating expenses, or correcting past underfunding. Most successful legal challenges to fee schedules turn on jurisdictions quietly loading deferred maintenance into their growth projections.
When the Fee Is Assessed and Paid
Most jurisdictions assess impact fees when a building permit is issued, so the developer pays before construction begins. Some calculate the amount earlier, at final plat approval, but hold collection until permit issuance.2Federal Highway Administration. Development Impact Fees A smaller number defer payment to certificate of occupancy or to permanent financing closing, sparing the developer from carrying the cost through construction.
Timing shapes project budgets. Fees due at permit issuance raise up-front capital requirements and construction loan costs. Builders working in phases should confirm whether the fee schedule in effect at each permit controls, or whether a vesting agreement locks in the rate from an earlier approval. Fee schedules get updated, and a rate increase between phases can change project economics substantially.
Rules on Holding and Spending the Money
Collecting the fee is only half the legal obligation. How the money is held and spent faces equal scrutiny.
Segregated Accounts
Enabling legislation typically requires funds for each capital facility category to sit in a separate account, not mixed with other revenue or with fees for different infrastructure types.3Federal Highway Administration. Value Capture – Development Impact Fees and Other Fee-Based Development Charges Road fees go into a road fund, park fees into a park fund. Money collected in a northern service district stays in that district’s account. Sweeping impact fee revenue into the general fund or spending it on unrelated projects in another part of the jurisdiction violates the earmarking requirement and can trigger mandatory refunds.
Deadlines and Refunds
Impact fees cannot sit unspent forever. State laws commonly require the jurisdiction to spend the money on the designated project within a set period, often five to six years, or make formal findings justifying continued collection. Miss the deadline without action, and the unspent fees plus accrued interest must be refunded to the current property owner, who is not necessarily the developer who paid. Impact fees also cannot generate revenue beyond their proportionate share of the improvements they fund.1Federal Highway Administration. Development Impact Fees / Mobility Fees This refund mechanism is the main enforcement tool keeping jurisdictions honest about actually building what they promised. Many states also require annual public reports for each account.3Federal Highway Administration. Value Capture – Development Impact Fees and Other Fee-Based Development Charges
Constitutional Limits
Three U.S. Supreme Court decisions define what governments can demand from developers. The cases originally addressed permit conditions like land dedications, but they now apply with equal force to legislatively adopted fee schedules.
Essential Nexus
In Nollan v. California Coastal Commission, the Court held that a condition attached to a land-use permit is valid only if it substantially furthers the same government interest that would justify denying the permit.4Justia. Nollan v. California Coastal Commission The fee has to connect logically to a real problem the development creates. A road fee is valid because new homes generate traffic. Charging a homebuilder for a public art installation would fail this test.
Rough Proportionality
Dolan v. City of Tigard added a second requirement: even when the connection is legitimate, the amount charged must be roughly proportional to the scale of the actual impact.5Justia. Dolan v. City of Tigard, 512 U.S. 374 (1994) No precise formula is required, but the government must make some quantified showing that the fee matches the burden. A $50,000 road fee on a single-family home generating 10 daily trips will face far more skepticism than the same fee on a shopping center generating thousands.
No Legislative Shield
For years, many courts protected legislatively adopted fee schedules from Nollan/Dolan review, reasoning those tests applied only to case-by-case administrative decisions. Sheetz v. County of El Dorado ended that distinction in 2024. The Court unanimously held that the Takings Clause does not distinguish between legislative and administrative permit conditions.6Justia. Sheetz v. El Dorado County, 601 U.S. ___ (2024) Every fee schedule in the country now faces essential nexus and rough proportionality review. Jurisdictions that used to rely on the legislative exemption may need to revisit whether their fee studies hold up.
Read together, these three decisions form the dual rational nexus test. First, a direct link must exist between the new development and the need for additional infrastructure. Second, the fee must be proportional to the benefit the development receives. A fee that fails either prong can be struck down as an unconstitutional taking.
Exemptions, Credits, and Waivers
Not every project pays the full schedule. Many jurisdictions offer full or partial exemptions for affordable housing. Some waive fees automatically for projects meeting income targets; others require a formal application with documentation of affordability commitments. Some cities cap annual exemptions to limit revenue losses. Others restrict eligibility to nonprofit developers. Replacement structures and minor renovations that add no new demand on public systems are also typically excluded. Rebuilding a house that burned down generates no new trips and no new sewer demand.
Credits work differently. When a developer voluntarily builds infrastructure, such as constructing a road segment, extending a sewer main, or dedicating parkland, the documented cost is credited against fees owed. The credit is confined to the matching category. Road construction credits against transportation fees, not parks or schools. If the improvement exceeds fees owed in that category, some jurisdictions let the excess credit be sold or transferred to other developers in the same service area.
Full waivers are rare because the jurisdiction has to absorb the infrastructure cost. They usually come through negotiated development agreements for large or economically significant projects, where the local government decides the jobs, tax base, or revitalization outweigh the lost revenue. Unlike published exemption criteria, waivers tend to be one-off legislative decisions and face heavier political scrutiny.
Who Actually Pays
Developers write the check, but they rarely absorb the cost. Empirical research has found that each dollar of impact fees increases new home prices by somewhere between $0.25 and $3.00, depending on local market conditions, housing supply elasticity, and competition from neighboring jurisdictions. In competitive markets with elastic supply, developers absorb more because raising prices would push buyers elsewhere. In constrained markets with scarce land and strong demand, the full fee (and sometimes more) passes to the buyer, because the fee itself restricts supply. Existing homes are pulled up too. One study found that fees increased existing home prices by more than they increased new home prices, as supply-side effects rippled through the local market.7U.S. Department of Housing and Urban Development. Impact Fees and Housing Affordability
Challenging an Assessment
A developer who believes the fee exceeds the project’s proportional impact can challenge it. The process usually starts with a written protest to the local government within a window set by state law, often 30 to 90 days after assessment. Missing the deadline can waive the right to challenge.
The protest needs technical evidence, not just disagreement. An independent traffic study, an engineering analysis, or comparable data showing that the standard schedule overstates the actual impact. A warehouse generating minimal traffic, for instance, might challenge a transportation fee calculated with generic commercial trip rates rather than warehouse-specific figures.
If the administrative process does not resolve the dispute, the challenge can go to court. After Sheetz, the constitutional argument is stronger, because even a legislatively adopted schedule has to satisfy nexus and proportionality.6Justia. Sheetz v. El Dorado County, 601 U.S. ___ (2024) Litigation is expensive and slow, so most disputes settle at the administrative stage, often through an adjusted fee or a credit arrangement for developer-built improvements.