Florida Save Our Homes Portability Calculator

How this calculator works

Florida's Save Our Homes (SOH) cap is one of the few unalloyed wins in the Florida tax code for long-term homeowners — and one of the most misunderstood. The cap, enshrined in Article VII § 4(d) of the Florida Constitution and implemented through F.S. § 193.155, limits annual increases in the assessed value of a homestead to the lesser of 3% or the year-over-year change in the CPI-U. After a few years of rising markets, the gap between a homestead's just market value and its capped assessed value can run into six figures — every dollar of which is property tax the homeowner is not paying. Florida calls this gap the SOH differential.

For decades, that benefit was lost the moment a homeowner sold and moved within Florida. The new homestead reset to just market value on the next tax roll, and the homeowner started accumulating a new differential from zero — a meaningful disincentive against in-state moves, particularly for retirees downsizing or growing families upsizing.

That changed with Amendment 5 of 2008, which added subsection (8) to F.S. § 193.155. Portability lets a homeowner carry the SOH differential — capped at $500,000 — from a prior Florida homestead to a new Florida homestead. The mechanism is the Florida Department of Revenue's Form DR-501T, filed with the new county property appraiser by March 1 of the tax year the homeowner wants the portability to apply.

This calculator runs the four key portability questions:

1. What is my SOH differential? Prior just market value minus prior assessed value.
2. How much of it can I port? The lesser of the differential or $500,000. If the new homestead is less expensive than the prior one (a downsize), a proportional share. If equal or more expensive (a lateral or upsize), the full lesser-of figure.
3. What is the new homestead's assessed value after portability? New just market value minus the ported amount.
4. What does that save me in property taxes — this year, over 10 years, over 20 years? Ported amount times millage rate divided by 1,000 for year-1; the SOH cap (3% or CPI, whichever is lower) governs the year-over-year growth of the gap, and the cumulative savings compound as the gap widens.

Upsize, downsize, lateral — the proration that catches everyone

The upsize/downsize distinction is the most common surprise for first-time portability filers. F.S. § 193.155(8)(b) lays it out:

• Upsize (new just market value greater than or equal to prior just market value): port the full lesser of differential or $500,000.
• Downsize (new just market value under prior just market value): port a proportional share equal to (new just market value ÷ prior just market value) times the lesser of differential or $500,000.

The proration prevents a windfall: if a Floridian sold a $600,000 home with a $400,000 differential and bought a $200,000 home, porting the full $400,000 would zero out the new home's assessed value entirely, which would be a tax-policy absurdity. So instead, the homeowner ports (200 ÷ 600) times $400,000 = $133,333. The new $200,000 home has an assessed value of $66,667. Still a meaningful benefit, just not the full benefit.

Lateral moves (new just market value equal to prior just market value) are treated the same as upsizes — the full lesser-of figure ports.

A worked example

A long-time Florida homestead, $300,000 just market value, $200,000 assessed value — a $100,000 SOH differential built up over 12 years of steady appreciation under the 3% cap. The homeowner sells and buys a new homestead for $700,000.

• SOH differential: $300,000 - $200,000 = $100,000.
• Statutory cap: $500,000 (not reached). Capped differential = $100,000.
• Move type: Upsize ($700,000 is more than $300,000). Proration factor = 1.0.
• Portable amount: $100,000.
• New homestead assessed value after portability: $700,000 - $100,000 = $600,000.
• Year-1 property tax savings at 20 mills: $100,000 times 0.020 = $2,000.
• 10-year cumulative savings (assuming 4% appreciation, with the gap growing at the 3% SOH cap each year): roughly $23,000.
• 20-year cumulative savings: roughly $54,000.

The $2,000 year-1 number is the most concrete: that is real, immediate cash a Florida homeowner does not write to the county tax collector because of portability. The 20-year cumulative number is what makes the math feel decisive — over the typical hold period for a Florida primary residence, portability can recover the closing costs and the documentary stamp tax of the move and then some.

A downsize counter-example

Same homeowner, same $100,000 differential, but moves to a $200,000 condo instead of the $700,000 single-family.

• Move type: Downsize ($200,000 is under $300,000). Proration factor = 200,000 / 300,000 = 66.7%.
• Portable amount: $100,000 times 0.667 = $66,667.
• New homestead assessed value after portability: $200,000 - $66,667 = $133,333.
• Year-1 property tax savings at 20 mills: $66,667 times 0.020 = $1,333.

A meaningful savings, smaller than the upsize case, and arriving on a smaller property — so as a percentage of the new property's tax bill, often a bigger relative impact for the retiree who is downsizing into a smaller footprint.

Where to find the inputs

Most Florida county property appraisers publish the relevant numbers on a public record card for every parcel:

• Prior homestead just market value, prior assessed value — TRIM notice (Truth in Millage), mailed every August to homestead owners, or the appraiser's online parcel record. The just market value is sometimes labeled "Just Value" or "Market Value"; the assessed value is sometimes labeled "Capped" or "Assessed."
• New homestead just market value — for a purchase, the contract price is typically what the property appraiser uses for the first tax roll, subject to adjustment after their independent valuation. For an existing property where the owner is establishing homestead for the first time, the appraiser's most recent just market value.
• Combined millage rate — TRIM notice for the new property, or the appraiser's published millage rates by parcel. Typical Florida combined rates (county general, school, municipal, special districts like fire and water management) run 18-22 mills. Coastal urban counties (Miami-Dade, Broward, Palm Beach) tend toward the higher end; inland and rural counties tend toward the lower.

What this calculator does not do

This calculator is a planning and screening tool. It does not:

• Substitute for filing Form DR-501T. The portability claim is not automatic. The new county property appraiser will not transfer the differential without an affirmative DR-501T submission, even if the standard homestead-exemption application has been filed at the new property.
• Handle multi-owner portability splits. When two co-owners (e.g., a divorcing couple) each take part of a shared homestead's differential to separate new homesteads, F.S. § 193.155(8)(c) governs the split. The calculator assumes a single-owner transfer; the split rule requires a separate analysis.
• Apply the homestead exemption. The standard $50,000 homestead exemption under F.S. § 196.031 reduces taxable value after portability has already adjusted the assessed value. It compounds with portability but is not modeled here. For a $700,000 new homestead with $100,000 portability, the assessed value is $600,000, the school taxable value is $575,000, and the non-school taxable value is $550,000.
• Account for additional caps. Non-homestead Florida properties have a 10% annual assessed-value cap under F.S. § 193.1554 (Amendment 1 of 2008). That cap is not portable. Senior-citizen additional homestead exemptions under § 196.075 may apply for owners over 65 with limited income; those are also not modeled here.
• Apply outside Florida. Save Our Homes and portability are Florida-only. Other states have different homestead-cap regimes (California Prop 13, Texas 10% cap, Oregon's Measure 50); none of them port to or from Florida.

How this page is maintained

The Save Our Homes framework has been stable since the 2008 portability amendment. The most recent material change was the 2020 legislative amendment to the filing window (extended briefly, then settled at two tax years effective with the 2021 tax roll). We monitor each Florida legislative session for changes to F.S. § 193.155 and related statutes. The $500,000 cap, the 3% annual SOH cap, and the proration formula in subsection (8) have been unchanged since the original 2008 amendment.

Last reviewed: 2026-05-15 against F.S. § 193.155, F.S. § 193.155(8), Florida Constitution Article VII § 4(d), and Florida DOR Form DR-501T.