Key Biscayne, FL: Property Tax Guide

One Bill, Multiple Governments

Every property on Key Biscayne pays into Miami-Dade County's countywide millage, which funds general county operations and, through a separate school-district component, Miami-Dade County Public Schools -- and that county-and-school total applies uniformly across the county regardless of which specific municipality, or unincorporated area, a parcel sits in. Miami-Dade County's total millage has run in the high-teens of mills per $100 of assessed value in recent tax years, with a substantial share of that dedicated to the school levy, per the Florida Department of Revenue's official county tax rate schedules and the Miami-Dade County Property Appraiser's own published millage tables.

On top of that county-and-school layer, the Village of Key Biscayne -- incorporated as its own municipality on June 18, 1991 -- sets and adds its own separate municipal operating millage to fund Village government, the Village Police Department, and local services, exactly as the City of Miami Beach, the City of Coral Gables, or any other Miami-Dade municipality does with its own rate. This page does not state the Village's exact current adopted millage figure, since it could not be independently confirmed at a level this page treats as settled current fact -- Village budgets are adopted annually and the rate can move year to year. Pull the exact combined current rate and bill for a specific parcel directly from the Miami-Dade County Property Appraiser's own online tax estimator, or call the Village of Key Biscayne's Finance Department directly.

Save Our Homes: A Real Benefit, Reserved for Primary Residences

Florida's Save Our Homes constitutional amendment caps the annual growth in assessed value on a homesteaded property -- meaning an owner's actual, permanent, primary residence with a filed homestead exemption -- at the lesser of 3% or the prior year's change in the Consumer Price Index. Over years of ownership, that cap can create a substantial and growing gap between a homesteaded property's taxable assessed value and its true market value, since Key Biscayne's real estate has appreciated meaningfully faster than 3% a year in most recent cycles. It's one of the more valuable long-term tax benefits available anywhere in Florida, but it only helps an owner who actually lives in the home as their genuine, permanent primary residence.

That qualifier matters enormously on Key Biscayne specifically. A market this heavily weighted toward second homes, international buyers, and investment property means a large share of the island's owners simply don't qualify for Save Our Homes at all -- a foreign national's vacation residence, an investor's rental unit, or a snowbird's winter home with a primary residence filed elsewhere generally does not carry a Florida homestead exemption. Don't assume a listing's currently displayed assessed value reflects any Save Our Homes-capped, below-market number; a large share of Key Biscayne inventory is taxed at or near full non-homestead assessed value already.

The Non-Homestead 10% Cap: The More Common Case Here

For property without a homestead exemption -- likely the more typical Key Biscayne case given the island's second-home and investment-heavy buyer pool -- Florida's separate non-homestead assessment cap, created by a January 2008 constitutional amendment, limits annual assessed-value growth to 10% for county and municipal levies (the school-board portion of the bill is excluded from this cap and can rise without that 10% limit). That cap applies broadly to second homes, rental property, vacant land, and commercial property, functioning as the default protection for most owners on this island rather than the more generous Save Our Homes cap reserved for genuine primary residences.

Critically, the non-homestead cap resets at sale. Florida law requires a county property appraiser to reassess non-homestead property at full current market value in the year following a sale, meaning the 10% cap only limits increases from that new, post-sale baseline going forward -- it does not carry a long-held seller's artificially low, capped assessment over to a new buyer. A Key Biscayne property that's changed hands infrequently, with its assessed value capped well below current market value for years under the prior owner, can produce a large, one-time jump in assessed value -- and tax bill -- in the year immediately after you close on it.

Portability: Only Between Primary Residences

Florida's homestead portability provision allows an owner to transfer some or all of an accumulated Save Our Homes benefit from a prior Florida homestead to a new one when they move -- but only between genuine primary residences with filed homestead exemptions, and only one homestead exemption is allowed per household at a time. Portability has no application to buying a Key Biscayne property as a second home or investment while keeping a homestead exemption filed elsewhere; the mechanism is built for someone actually relocating their primary residence, not for adding a vacation property. Anyone genuinely making Key Biscayne their full-time primary residence for the first time may be able to file a new homestead exemption and, if applicable, port savings from a prior Florida homestead -- confirm the specific mechanics, filing deadlines, and required documentation directly with the Miami-Dade County Property Appraiser's office.

Annual Reassessment, No Other Smoothing

Outside of the homestead (Save Our Homes) and non-homestead (10%) caps described above, Florida applies no other systematic mechanism to smooth assessed-value growth. Miami-Dade County reassesses property values every year rather than on a multi-year cycle, meaning a property's taxable assessed value is revisited annually and constrained only by whichever cap -- if any -- applies to it. Given how sharply Key Biscayne real estate values have moved over the past several years, that annual reassessment cycle, combined with the full market-value reset that occurs the year after a non-homestead property sells, is one of the more consequential facts a new buyer needs to understand before finalizing a purchase budget -- the number on a current listing's tax history is very likely not the number the next owner will actually pay.

What This Means When You Budget a Purchase

Three things matter most in practice. First, don't anchor a tax budget to the seller's current tax bill or currently displayed assessed value -- unless the property becomes your own homestead, Florida law resets it to full current market value the year after you buy, and on a long-held Key Biscayne property that reset can be a meaningful jump from a seller's older, capped assessment. Second, run an actual estimate for the specific parcel through the Miami-Dade County Property Appraiser's own online tax estimator, which correctly layers county, school, Village, and any applicable special-district millage for that exact address -- a blended countywide or island-wide average figure is not precise enough for a Key Biscayne purchase given how the Village's own municipal rate factors in. Third, if the property will genuinely be your primary residence, file for homestead exemption before Florida's filing deadline (generally March 1 of the qualifying year) and ask the Property Appraiser's office directly whether portability applies from any prior Florida homestead. None of this is tax advice -- a Florida real estate attorney or CPA familiar with Miami-Dade property tax mechanics should review the actual numbers on any specific purchase before you rely on them.