The Mitigation Fee Act: bounding the impact-fee line

Impact fees are usually the second-largest soft-cost line in a California multifamily budget, and the Mitigation Fee Act (Gov. Code §§ 66000–66025, archived with the school-fee chapters) is the statute that disciplines them. Every fee must be supported by findings connecting its purpose, its use, and a reasonable relationship between the amount charged and the burden your project actually creates — the statutory codification of the constitutional nexus/proportionality line running from Nollan/Dolan through Sheetz (2024), which applied it to legislatively set fees too.

For underwriting, three practical levers matter most: what the fee schedule lawfully is (frozen by your SB 330 preliminary application), when you must pay it, and how to preserve a refund claim when a fee looks unlawful.

Since AB 602 (§ 66016.5, 2021), new or increased fees need a published nexus study identifying the existing level of service, the capital improvements to be funded, and the proportionate share allocated to new development; residential fees are to be scaled by square footage unless findings justify otherwise; and studies must be adopted at noticed hearings and refreshed on a defined cycle.

• Underwriting watch-outs:
• Per-unit flat fees on small units are the classic AB 602 vulnerability — a 500 sq ft studio paying the same as a 1,400 sq ft three-bedroom invites challenge.
• Fee schedules must be publicly posted (§ 66016.3 transparency rules); demand the current schedule and the underlying nexus study during feasibility.
• ADUs under 750 sq ft are statutorily fee-exempt; larger ADUs pay proportionately (see the ADU guide).

Section 66007 bars collecting most impact fees before final inspection or certificate of occupancy for residential projects — with carve-outs where funds are already appropriated for construction or the agency runs a lawful early-collection program (utility connection charges follow their own rules). Deferred payment is a real carry-cost benefit on 18–30 month builds.

• Underwriting watch-outs:
• An SB 330 preliminary application freezes the fee schedule; § 66007 sets the payment date. Together they bound both amount and timing.
• Cities sometimes condition permits on early payment beyond the statute — a negotiable (and protestable) point.
• "Fees" dressed as taxes or assessments (CFD special taxes, utility capacity charges) are outside the Act — classify each line item before assuming the protections apply.

To challenge a fee you must pay it under protest and file the § 66020 protest within 90 days of imposition, then sue within 180 days of the agency's notice. Miss the window and even an unconstitutional fee is generally unrecoverable.

Agencies must keep fee revenues in separate accounts, report annually, and every five years make findings re-justifying unexpended balances (§ 66001(d)) — absent findings, the remedy is refund to then-current owners. Occasional but real money.

• Practical sequencing:
• File a protective § 66020 protest whenever a fee looks disproportionate — it costs a letter and preserves the claim while the project proceeds.
• On acquisition of a recently completed asset, check whether refundable protest rights or 5-year-finding refunds run with the property.