Selling your business: 7 tax mistakes owners make
The 7 costliest tax mistakes owners make when selling a business: retirement relief, social levies, shares or goodwill, high-income surtax, contribution-sale and vendor financing.
Expert note: This article was written by our chartered accountancy firm. Information is current as of 2026. For a personalised review of your situation, contact us.
Quick answer. The costliest tax mistakes when selling a business rarely come from the calculation itself, but from timing and confusing the applicable regimes. Mishandling retirement, forgetting social levies, mixing up share and asset sales or overlooking the high-income surtax can add tens of thousands of euros, when a few months of planning would have prevented it.
Selling your company is often the financial transaction of a lifetime. Yet many owners treat the tax side as a last-minute formality, once the price is agreed and the deal almost signed. That is exactly when it is too late to act: most tax levers in a sale must be prepared 12 to 24 months ahead, sometimes more.
This article reviews the seven tax mistakes we see most often in transfer files, and a concrete fix for each. The goal is not to cut tax at any cost, but to secure the choice and avoid avoidable losses. To frame the value beforehand, see also our method to value your business before a sale.
The 7 mistakes and their fixes at a glance#
| # | Common mistake | Tax consequence | The fix |
|---|---|---|---|
| 1 | Not planning the retirement relief | Possible loss of the 500,000 € relief | Set retirement within the 2-year window |
| 2 | Believing the relief wipes out all tax | Social levies due on the whole gain | Set aside 18.6% on the full gain |
| 3 | Mixing up share and asset sales | Wrong capital gains regime | Decide the sale type beforehand |
| 4 | Overlooking the high-income surtax | 3 to 4% extra tax | Build the surtax into the simulation |
| 5 | Misusing the contribution-sale (150-0 B ter) | Tax deferral lost or unsecured | Structure the holding before the sale |
| 6 | Underestimating tax with vendor financing | Tax due before the price is received | Plan the cash for the tax |
| 7 | Deciding alone and too late | Poor choice, expired levers | Simulate and decide 12 to 24 months ahead |
The 7 tax mistakes, one by one#
1. Not planning the retiring-owner relief#
The fixed relief of 500,000 € under article 150-0 D ter of the French tax code is one of the most powerful tools for an SME owner selling shares ahead of retirement. It applies whatever the chosen tax method, flat tax or progressive scale. But it carries strict conditions, and the trickiest one is timing.
The owner must cease their duties and claim their retirement rights within two years before or after the sale. A gap of a few months between the sale and the effective start of the pension is enough to forfeit the relief. This timing mechanism is covered in our article on capital gains exemptions on a sale.
Our reading. The 500,000 € relief does not trigger on its own: it is prepared. Have your pension fund confirm the exact possible liquidation date before you sign anything. It is the alignment of dates, not merely their existence, that secures the benefit.
2. Believing the 500,000 € relief wipes out all tax#
This is probably the most widespread confusion. The 500,000 € relief applies only to the income tax portion, namely the 12.8% of the flat-rate tax. The social levies of 18.6%, raised on 1 January 2026, remain due on the entire capital gain, relief or not.
In concrete terms, an owner with a 600,000 € gain who fully benefits from the relief still owes social levies on the full 600,000 €, and income tax on the portion above 500,000 €. The table below summarises what the relief covers and what it does not.
| Tax component | Does the retirement relief cover it? |
|---|---|
| Income tax (12.8% under the flat tax) | Yes, on the first 500,000 € of gain |
| Social levies (18.6%) | No, due on the entire gain |
| High-income surtax (3 to 4%) | No, based on the reference taxable income |
To turn these rates into a net amount actually received, use our method to calculate the net price after tax on a business sale.
3. Confusing a share sale with a goodwill (asset) sale#
Selling the shares of your company has nothing to do, fiscally, with selling the goodwill held by that company. A share sale falls under private capital gains, with the flat tax at 31.4% and, where applicable, the retirement relief. A goodwill sale falls under professional capital gains, with its own exemptions.
On a goodwill sale, two regimes coexist: article 151 septies, based on the level of revenue (thresholds of 250,000 € and 90,000 €), and article 238 quindecies, which exempts the gain up to 500,000 € of asset value, tapering up to 1 M€. The choice between selling shares or selling goodwill therefore changes the bill dramatically, and also the buyer's situation. Our guide to choosing the right transfer method details this trade-off.
Trade-off. Share sale or asset sale: there is no universal answer. A share sale is often more favourable to a seller eligible for the retirement relief; an asset sale may suit a buyer wishing to leave the company's liabilities behind. The decision lies at the crossroads of your personal situation and the buyer's expectations, never on a single criterion.
4. Overlooking the high-income surtax on a large gain#
A large gain inflates the year's reference taxable income, and often triggers the high-income surtax of article 223 sexies of the French tax code. It runs at 3%, then 4% on the upper bands, above 250,000 € of reference taxable income for a single person and 500,000 € for a couple.
This surtax adds to the taxation of the gain and regularly slips past owners who think only in flat-tax terms. On a sale worth several million euros, the surtax is far from anecdotal and must be built into the very first simulation.
5. Misusing or ignoring the contribution-sale (150-0 B ter)#
When an owner plans to reinvest the proceeds of the sale, the contribution-sale of article 150-0 B ter can allow a deferral of tax on the gain. The principle: contribute the shares to a holding you control before the sale, then sell the shares through that holding. The deferral is maintained if the holding reinvests a substantial portion of the proceeds in an eligible activity, within a set timeframe.
It is a demanding technique. The order of operations is decisive: if the sale precedes the contribution, the regime does not apply. The portion to reinvest and the deadlines have also changed, notably for sales after 21 February 2026. For wealth structures of this kind, see our holding taxation engagements.
The underestimated risk. The contribution-sale and the retirement relief do not combine freely: you generally choose one or the other depending on the goal, reinvest or spend the capital. Trying to stack both without prior analysis often forfeits the benefit of both.
6. Underestimating the tax with vendor financing#
Vendor financing, where the seller accepts staged payment of the price, is a useful negotiating tool. But on the tax side, the gain is in principle taxed in the year of the sale, on the full agreed price, even if part is received later. The owner may therefore have to pay the tax before receiving the entire price.
A tax-spreading mechanism exists under conditions, which we present in our article on vendor financing and tax spreading. Without this planning, vendor financing can create a severe cash-flow strain in the year of the sale.
In practice. If you are considering vendor financing, first quantify the tax due in the year of sale, then compare it with the negotiated payment schedule. A sale partly paid over three years with the full tax due in year 1 is not the same deal as a cash payment.
7. Deciding alone, with no figures or trade-off, and too late#
The last mistake encompasses all the others: arriving at your adviser with a deal already drafted, simply asking to compute the tax. By then, the trade-off between flat tax and progressive scale, the timing of retirement, the possible structuring of a holding or the securing of vendor financing can no longer be steered.
| Tax method for the share gain | What it implies |
|---|---|
| Flat tax at 31.4% | Single, simple rate, retirement relief applied to the income-tax portion |
| Progressive income tax scale (by global election) | May be attractive depending on the band, but the election applies to all capital income of the year |
2026 watch points. The rise of social levies to 18.6% on 1 January 2026, the extension of the 150-0 D ter relief to 31 December 2031, and the change in reinvestment conditions for the contribution-sale for sales after 21 February 2026 are all parameters to build into an up-to-date simulation. An analysis dated from last year is no longer reliable.
The checklist to prepare a smooth sale#
- Have the business valued and set a realistic price range
- Choose the sale type: shares or goodwill
- Check eligibility for the retirement relief and the possible pension start date
- Set aside the 18.6% social levies on the entire gain
- Assess exposure to the high-income surtax from the projected reference taxable income
- Decide, where relevant, on a contribution to a holding before any firm negotiation
- Plan the cash for the tax in case of vendor financing
- Compare flat tax and progressive scale with a figures-based simulation
- Secure a vendor tax due diligence before presenting the file to the buyer
For the last point, see our article on vendor tax due diligence, and for end-to-end support, our growth strategy and valuation engagements.
Special cases#
Several situations call for specific treatment. A family transfer may use the Dutreil pact, whose conditions are unrelated to a sale to a third party: our complete guide to the Dutreil pact details this regime. A partial sale of shares, which does not cover all or the majority, may forfeit the retirement relief. Holding via a company subject to corporate tax follows a different logic, calling for the analysis of a tax expert.
Common case#
In transfer files, one of the most frequent sticking points is the retirement timeline. An owner once consulted us after selling his SME, convinced he would liquidate his pension "right away". Between the administrative delays of his fund and a personal postponement, the effective start of his rights fell beyond the two-year window. The 500,000 € relief was lost. The income tax, which would have been largely neutralised, had to be paid in full. A few weeks of planning and a simple date check with the fund would have changed the outcome.
Frequently asked questions
What are the main tax mistakes when selling a business?+
The costliest are poor retirement timing, forgetting the social levies due on the whole gain, confusing a share sale with an asset sale, overlooking the high-income surtax, misusing the contribution-sale, underestimating vendor financing, and the lack of a figures-based simulation upfront.
Does the 500,000 € relief apply with the flat tax?+
Yes. The article 150-0 D ter relief for a retiring owner applies whatever the tax method, flat tax or progressive scale. But it covers only the income-tax portion, namely the 12.8% of the flat tax, and not the social levies.
Are social levies due despite the retirement relief?+
Yes, in full. The 18.6% social levies, raised on 1 January 2026, remain due on the entire capital gain, whether or not you benefit from the 500,000 € relief. The relief only neutralises the income-tax portion, never the social portion.
Should you sell the shares or the goodwill?+
The two follow different regimes. A share sale falls under private capital gains, with flat tax and a possible retirement relief. A goodwill sale falls under professional capital gains, with the exemptions of articles 151 septies and 238 quindecies. The choice depends on your situation and the buyer.
Does vendor financing change the tax due?+
Vendor financing does not reduce the tax: the gain is in principle taxed in the year of sale on the full price, even if paid in instalments. You may therefore owe the tax before receiving everything. A spreading mechanism exists under conditions, to be secured upfront.
When should you start preparing the tax side of a sale?+
Ideally 12 to 24 months ahead, sometimes more. Most levers, retirement timing, holding structuring, choice of sale type, are no longer actionable once the deal is drafted. An early figures-based simulation lets you decide calmly rather than absorb the bill.
Key takeaways#
- The 500,000 € retirement relief (tax code art. 150-0 D ter, extended to 31 December 2031) covers only the income-tax portion, not the social levies.
- The 18.6% social levies, raised on 1 January 2026, remain due on the entire gain, whatever the situation.
- Share sales and goodwill sales follow two distinct capital gains regimes: the trade-off is made upfront.
- The 3 to 4% high-income surtax and the contribution-sale (150-0 B ter) are often-forgotten parameters, to build into an up-to-date simulation.
- The tax side of a sale is prepared 12 to 24 months ahead, with a figures-based simulation and a flat-tax versus scale trade-off, never under pressure.
This article provides a general framework. Each sale has its own specifics, and a suitable decision requires reviewing your situation, your documents and the law in force at the date of the transaction. To gauge the stakes concretely, you can rely on the role of the chartered accountant in a sale.
Article written by Samuel HAYOT
Chartered Accountant, registered with the Institute of Chartered Accountants.
Regulated French accounting and audit firm based in Paris 8, built to support companies across France with a digital and decision-oriented approach.
Sources
Official and operational sources cited for this page.
This topic is part of our service Business valuation & M&A advisory in France
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