Compliance asserted from a miscalculation is worse than no compliance check at all, because it is confidently wrong, and the confidence goes in the minutes. The 20 percent cap is a one-line rule with a four-way trap: the rule is easy, the base is where boards go wrong.
What the law says
Civil Code § 5605(b): without membership approval, the regular assessment may not increase more than 20 percent over the regular assessment for the immediately preceding fiscal year. That phrase is the whole exam.
In this guide
Failure one: the gross-expense base
The regular assessment is not the expense total. It is expenses minus offsetting income: interest, leases, fees, the cell tower. Run the cap math off gross expenses and the check is fiction in both directions, an inflated base one year, an inflated increase the next. Compare net to net: last year's regular assessment as levied against this year's as derived. (And note the compounding error: offsetting income that was forgotten at drafting, input three of Seven Inputs Your HOA Budget Ignored, inflates the assessment and corrupts the cap math in the same stroke.)
Failure two: specials folded into the base
Last year the association levied a special assessment. This year someone computes the cap from "what members paid last year," specials included. That manufactures ceiling room that does not exist: the statute's base is the regular assessment only. A special is a separate, separately capped instrument, budgeted perhaps, but never part of the regular base.
Failure three: the per-unit misreading
The cap applies to the association's total regular assessment, derived from the budget net of offsetting income. It is not a per-unit guarantee that no individual line moves more than 20 percent. The corollary matters more than the rule: an allocation correction, fixing a split that never matched the CC&Rs, can lawfully move one unit's assessment more than 20 percent while the association stays fully compliant. That owner conversation is exactly where the derivation thread earns its keep: you show the clause and the math, not an apology (the correction itself is covered in When Equal Isn't Equitable: Audit Your Split Against Your Documents).
Failure four: the pre-revision base
The association passed a lawful mid-year revised budget. Next year's cap measures from the revised regular assessment, the level in force at year end, not the originally adopted one. One boundary: this holds if the revision itself stayed within the board's 20 percent authority when passed. A lawful revision moves the floor; an unlawful one cannot manufacture a higher base. (When and how to revise is its own piece: A Budget You Can't Revise Is a Budget You'll Violate.)
The precondition that voids everything
From the manager's side, § 5605(a) is the deadline that outranks the math: the board's authority to increase without a vote exists only if the annual budget report went out 30 to 90 days before the fiscal year (§ 5300). A late packet does not shrink the increase. It voids it.
Deadline discipline and increase authority are the same thing.
(Genuine emergencies have their own route: § 5610; Can My HOA Raise Assessments Without My Vote? covers it from the owner's side.)
The worked calculation
Last year's regular assessment: $400 per month equivalent. Ceiling this year: $480. The budget, built line by line and net of offsetting income, derives $470: adopt it, board authority alone. Had it derived $495, the increase goes to the membership for approval by a majority of a quorum. The order of operations is the entire discipline:
The chain, in order
Expenses − offsetting income = regular assessment → allocated per the documents → per-unit shares → and only then, the cap check.
The cap is a ceiling on a derived outcome. It is never the method for setting dues, and a board that runs the chain in this order finishes every season the way this piece intends: protected.
In the interest of transparency: this is the gap my company works on. We offer a free, easy-to-use tool governed by your association's own documents. It ensures every budget line is properly coded, who is responsible and on what basis it is shared, as the documents direct, or as an explicit board decision where the documents leave that to the board. The math underneath is deterministic. The method above works with or without it.
Sources: Cal. Civ. Code § 5605 (caps and precondition) · § 5300 (budget report window) · § 5610 (emergencies).
