Key Colony Beach, FL: Property Tax — a Small City's Own Layer

A Genuinely Separate City, Sitting Inside Marathon's Footprint

Key Colony Beach is a small, separately incorporated municipality that sits as its own distinct island in the Middle Keys -- geographically enclosed by Marathon's area, but legally and administratively its own city, with its own commission-and-administrator government. It was already an established, separate incorporated city well before Marathon incorporated in 1999, and it was not absorbed into Marathon's new city government at that time. For a property owner, that structural fact translates directly onto the tax bill: a parcel inside Key Colony Beach's city limits is taxed under the City of Key Colony Beach's own adopted millage, set through the city's own annual budget process, stacked on top of Monroe County's countywide millage and the Monroe County School Board's millage -- the same three-layer arrangement that applies inside any of Monroe County's incorporated towns.

That third, municipal layer is what funds the parts of local government that are visibly the city's own rather than the county's: Key Colony Beach maintains its own police department (KCBPD), distinct from the Monroe County Sheriff's Office; its own building department and code-enforcement function, with its own permitting portal separate from the county's; and its own city hall and commission-administrator staff. A small, purely residential city still has to budget for a police department, a building department, and a city hall the same way a larger one does -- the running costs just get spread across a much smaller tax base.

How That Differs From Unincorporated Key Largo, and From Marathon's Own Layer

This site's Key Largo property-tax page covers the opposite case in the same Middle Keys stretch: Key Largo is unincorporated, with no city government and no municipal millage at all, so an owner there pays only the countywide and school-board layers, with land-use and permitting handled directly by Monroe County. Key Colony Beach is the other end of that same structural spectrum -- a small city that chose (or rather, already existed as) its own incorporated municipality, adding a municipal layer that unincorporated Key Largo simply doesn't have.

Marathon, covered on its own page on this site, is also one of the five incorporated municipalities and levies its own City millage plus runs its own Building Permit Allocation System (BPAS) -- a much larger city with its own well-documented 2024 allocation crunch. Key Colony Beach's municipal layer is real in the same structural sense, but the city itself is far smaller, and this research pass did not confirm whether Key Colony Beach runs an equivalent BPAS-style allocation pool of its own (a 2024-2025 Keys Weekly headline about the city weighing a transfer of its own building rights to Marathon suggests it likely holds some form of transferable allocation, but the mechanics were not verified). This page isn't the place to re-walk Marathon's BPAS story in depth -- see this site's Marathon property-tax page for that.

The City's Own Millage Rate -- Not Stated Here, Because It Wasn't Confirmed

This page will not print a specific current millage rate for the City of Key Colony Beach, for the same reason this site's Key West, Marathon, Islamorada, and Key Largo pages don't print unconfirmed numbers for those jurisdictions: no specific, current mill figure for Key Colony Beach, and no assessed-value or tax-bill example, was confirmed against a fully-loaded primary source in the research behind this page. Guessing at a number here would be worse than disclosing the gap.

The right places to get a confirmed, current figure are the Monroe County Property Appraiser's office, which maintains countywide millage information for every taxing jurisdiction in the county including Key Colony Beach, and the City of Key Colony Beach's own government directly, which sets and publishes its adopted millage each budget cycle as part of Florida's Truth-in-Millage (TRIM) process. A specific parcel's own TRIM notice, mailed annually, is the most reliable source of all for what that property actually owes -- and it's also the clearest confirmation that a Key Colony Beach parcel carries all three lines: county, school board, and city.

The Statewide Florida Framework Still Applies Underneath All of This

Underneath the city's own millage, the same statewide Florida rules already documented in depth on this site's Key West and Florida Keys hub pages apply identically in Key Colony Beach: no state personal income tax, a homestead exemption worth up to $50,000 for a permanent primary residence, a Save Our Homes cap limiting how fast a homesteaded property's assessed value can rise each year, and a separate, less generous 10% annual cap on non-homestead property. None of that is Key Colony Beach-specific, so it isn't re-walked in depth here -- see this site's Key West property tax page for the full mechanics, which apply the same way to any homesteaded or non-homesteaded property in Key Colony Beach.

What This Page Does Not State, and Why

This page deliberately does not state a current City of Key Colony Beach millage rate, a combined mill figure for any specific parcel, an effective tax-rate percentage, or any dollar comparison to Key Largo's, Marathon's, or another Keys jurisdiction's bill, because none of those were confirmed against a fully-loaded primary source in the research behind this page. That's a disclosed gap, not an oversight. This page is independent research, not tax or legal advice, and nothing here should be used to budget a specific tax bill or to assume a specific parcel's buildability. Confirm current figures directly with the Monroe County Property Appraiser's office, the City of Key Colony Beach's own government for city-specific budget and permitting questions, and a licensed Florida tax professional or attorney before making any purchase, budgeting, or tax-planning decision.