Property tax reassessment: how it really works and what it costs

Property tax reassessment: the hidden driver in your buy or rent maths

When people compare whether to buy or rent, they usually focus on the mortgage rate (around 3.6% in 2024), the purchase price or the initial rent. Yet one line in the budget can quietly eat tens of thousands of euros over 20–25 years: property tax reassessment.

Our buy or rent simulator includes a specific parameter for this: taux_revalorisation_taxe_fonciere_annuelle (annual property tax increase). Understanding how it works is as important as knowing your loan rate, notary fees, expected rent increases or your investment rate of return.

1. How property tax is actually calculated

1.1 Two building blocks: rental values and local tax rates

In France, property tax (taxe foncière) is based on:

• The cadastral rental value of your home, i.e. a theoretical annual rent assigned by the tax authorities.
• The tax rates voted by your municipality, inter-municipal body and department.

A simplified formula looks like this:

Property tax = (Rental value × allowance) × (sum of local tax rates)

For residential property, the allowance is often 50% of the rental value. Example:

• Cadastral rental value: €4,000 / year
• 50% allowance → taxable base: €2,000
• Total local tax rate: 30%

Property tax = €2,000 × 30% = €600

1.2 Automatic revaluation of rental values

Every year, rental values are revalued nationally using a coefficient linked to inflation. In 2023, this revaluation reached 7.1%; in 2024 it was 3.9%. In practice, your property tax can rise even if your city leaves its tax rate unchanged.

This is exactly what the simulator’s taux_revalorisation_taxe_fonciere_annuelle parameter models: a mechanical yearly increase in your property tax bill.

2. Annual property tax increase: what it means over time

2.1 Two drivers of growth

Your property tax can go up for two main reasons:

• National revaluation of cadastral rental values (partly indexed on annual inflation).
• Local decisions: your municipality and inter-municipal body can raise their tax rates.

In a serious buy or rent comparison, assuming a flat property tax is unrealistic. A reasonable modelling range is often 2% to 4% per year, but the right figure depends on your area’s history and future inflation.

2.2 Simple example: €1,200 property tax in year one

Imagine you buy a flat and your first-year property tax is €1,200. Test three assumptions for taux_revalorisation_taxe_fonciere_annuelle:

• Scenario A: 1% per year
• Scenario B: 3% per year
• Scenario C: 5% per year

After 20 years, your annual property tax becomes:

• A (1%): 1,200 × (1.01)²⁰ ≈ €1,464
• B (3%): 1,200 × (1.03)²⁰ ≈ €2,166
• C (5%): 1,200 × (1.05)²⁰ ≈ €3,183

The total paid over 20 years differs sharply:

• A (1%): about €25,200
• B (3%): about €32,000
• C (5%): about €40,000

Between an optimistic 1% and a pessimistic 5% assumption, the gap exceeds €14,000 over 20 years. That’s money you can’t use to repay principal faster or invest in ETFs or savings accounts at your chosen investment rate if you were renting instead.

3. Rental values: why your city matters more than you think

3.1 Huge differences between municipalities

Property tax amounts vary widely: some owners pay €450 per year, others more than €5,000. It depends on:

• The cadastral rental value of your home (size, category, area).
• Local tax rates voted by your authorities.
• Your local government’s budget needs and tax policy.

Two similar properties bought at the same price can generate very different property tax bills. In a buy or rent comparison, this difference can offset or cancel out benefits from a lower mortgage rate or a cheaper purchase price.

3.2 Numerical example: City A vs City B

Take two cities, same type of flat:

• City A: initial property tax €800, annual increase 2%.
• City B: initial property tax €2,000, annual increase 4%.

Over 25 years:

• City A: total ≈ 800 × ((1.02)²⁵ − 1) / 0.02 ≈ €26,000
• City B: total ≈ 2,000 × ((1.04)²⁵ − 1) / 0.04 ≈ €82,000

In City B, cumulative property tax over 25 years can equal more than 10% of an €800,000 flat. Any realistic buy or rent simulation must include this, just like notary fees (7–8% on existing property, 2–3% on new build) or agency fees (3–5%).

4. How inflation ties together tax reassessment and rent increases

4.1 Inflation: double impact on owners and tenants

Annual inflation hits several levers at once:

• It tends to raise cadastral rental values, pushing up property tax.
• It fuels rent increases via the French IRL index.
• It erodes the real cost of fixed-rate mortgage payments (around 3.6% today) and your outstanding debt.

If you buy, you are exposed to property tax reassessment, but your mortgage payment is usually fixed in nominal terms. If you rent, you avoid property tax but face rent revaluation and can invest your down payment at an assumed investment rate (for example 3–5% net) instead.

4.2 Example: owner vs tenant over 20 years

Simplified scenario for a comparable home:

• Purchase price: €300,000
• Notary fees: 8% → €24,000
• Down payment: €60,000
• Loan: €240,000 at 3.6% over 20 years
• Initial property tax: €1,500, annual increase 3%
• Initial rent: €1,100, annual increase 2.5% (IRL)
• Investment rate if renting: 4% per year net

Over 20 years:

• The owner pays roughly 1,500 × ((1.03)²⁰ − 1) / 0.03 ≈ €40,000 in property tax alone.
• The tenant avoids this tax but sees rent rise from ~€1,100 to about €1,800/month by the end of the period.

In a buy or rent comparison, the key question is: after 20 years, is your net home equity (after mortgage, insurance at ~0.25–0.45%, maintenance, property tax and any renovations) greater or smaller than the wealth you could build by investing your capital at the assumed investment rate while renting? The taux_revalorisation_taxe_fonciere_annuelle parameter is central to this equation.

5. How the buy-or-rent.net simulator models property tax reassessment

5.1 The taux_revalorisation_taxe_fonciere_annuelle parameter

In our simulator you input:

• Your initial property tax amount.
• The assumed taux_revalorisation_taxe_fonciere_annuelle, for example 2%, 3% or 4%.

The model then computes, year by year, your property tax and the cumulative amount over your holding period (often 15–25 years). This lets you compare:

• The full cost of owning (mortgage at the current loan rate, insurance, property tax reassessment, maintenance, renovation, purchase costs);
• With the full cost of renting (rent revalued using the IRL index) while investing your savings at the chosen investment rate.

This level of detail is what turns a gut-feel decision into a quantified buy or rent analysis.

5.2 Why you should test several reassessment scenarios

No one can predict future inflation or your city’s tax policy. What you can do is:

• Look up the last 10 years of property tax changes in your municipality.
• Run the simulator with several values for taux_revalorisation_taxe_fonciere_annuelle, for example 1%, 3% and 5%.

Comparing these scenarios shows you:

• At what property tax growth rate buying becomes less attractive than renting.
• How this interacts with other parameters: loan rate, investment rate, annual inflation, rent indexation.

This is exactly what the buy or rent tool is designed to do: show you, in euros, the impact of each assumption.

6. Reassessment, energy performance and renovations

6.1 Potential link with energy ratings

French rental values are being reformed and may increasingly factor in energy performance. Poorly rated homes (low DPE score) could see their cadastral rental values evolve differently, which would affect future property tax reassessment.

At the same time, renovation costs (insulation, windows, heating systems) have a dual effect:

• They increase the total cost of ownership in the short term.
• They may improve your home’s attractiveness, potential rent and resale value in the long term.

In a buy or rent framework, it makes sense to factor in:

• A realistic renovation budget;
• A cautious scenario for taux_revalorisation_taxe_fonciere_annuelle;
• And a realistic investment rate if you stay a tenant and invest your capital instead.

7. How to use property tax reassessment in your decision process

7.1 Practical steps

To integrate property tax reassessment into your buy or rent thinking, you can:

• Step 1: find the current property tax for the home you’re targeting (or a very similar one).
• Step 2: check historical increases in your area (official stats, local news).
• Step 3: choose a prudent taux_revalorisation_taxe_fonciere_annuelle, for example 3% if increases have been strong.
• Step 4: enter these figures in the simulator together with:
• loan rate (around 3.6%),
• borrower insurance rate,
• notary and agency fees,
• expected annual inflation,
• investment rate for your savings,
• annual rent increase based on the IRL index.

You then get a quantified projection of the net cost of owning versus renting over 15, 20 or 25 years.

7.2 Important disclaimer

The simulator’s outputs and the examples in this article rely on assumptions and averages. They are not personalised financial advice. Your own situation (income, assets, risk tolerance, mobility, family plans) can justify different choices even with similar numbers.

8. Bottom line: property tax reassessment can tip the scales

Over a 20–25 year horizon, property tax reassessment can add up to the price of a car, or even a small flat in some areas. Ignoring it in a buy or rent comparison seriously distorts the picture between:

• The full cost of owning (mortgage, insurance, notary and agency fees, maintenance, renovations, reassessed property tax);
• And the full cost of renting (inflation-linked rent, but invested savings at a realistic investment rate).

Rather than relying on rules of thumb, it is more robust to test several scenarios for taux_revalorisation_taxe_fonciere_annuelle, interest rates, inflation and portfolio returns, and see how the numbers evolve.

To quantify precisely how property tax reassessment affects your long-term budget and your buy or rent decision, simulate your situation on buy-or-rent.net.