A potential increase which arouses very real fear. During the examination of the Social Security budget for 2026 (PLFSS), deputies adopted an increase in the generalized social contribution (CSG) on capital income. If it was finally adopted, this increase would impact the rate of the single flat-rate levy (PFU), the famous flat tax, made up of 12.8% income tax and 17.2% social security contributions. This second component being increased to 18.6%, the entire flat tax would increase from 30 to 31.4%.
The result: heavier taxation for many of your investments subject to this flat tax: ordinary savings accounts, term accounts, home savings plans (PEL), life insurance, stock savings plans (PEA), etc. But from when? The expenditure and revenue voted on as part of the Budget apply in principle for the following year, which is why the two finance bills must be voted on before December 31, 2025.
Heavier taxation on your income received from this year?
However, there is great fear that this tax measure will in fact be retroactive. That is to say, it does not concern your investment income from 2026, but those received from this year. Recent history constitutes the main reason for concern: “During the last increase in the CSG, from 15.5% to 17.2%, as part of the 2018 PLFSS, the date of entry into force was provided for by law depending on the nature of the income. Thus, the capital gains on the sale of securities realized in 2017 and declared in 2018 had increased. recalls Nicolo Acquari, heritage engineer at Mirabaud.
In other words, the capital gains realized, for example, during the sale of shares in 2017, had been taxed at the new CSG rate in 2018. Which could happen again this year: “Clearly, if you received 1,000 euros in dividends this year, you receive 700: your establishment having withheld income tax of 12.8% and social security contributions of 17.2%. In the event of an increase in the CSG, you would also find, on your 2026 tax notice, the 1.4% increase in the CSG that you would have to pay. illustrates the heritage engineer.
The fear of a tax catch-up in 2026
Savers may therefore fear a “catch-up” during the spring 2026 declaration on their 2025 income. “In the absence of precision, income such as dividends and interest on which social security contributions are deducted at the time of their payments (in 2025, Editor’s note) could also be subject to the increase in the CSG (in 2026),” adds Nicolo Acquari. In addition, this would also be the case for the interest received on the euro fund part of your life insurance, on your PEL or a bank account. Because if their payment will take place from January 1, 2026, this interest will be collected for the year 2025.
And this, even if you pay little or no tax, or you have requested to be exempt from paying a deposit on your interest or dividends paid in 2025. Indeed, if we can avoid the “income tax” part of the flat tax, it is impossible to escape social security contributions, and therefore their increase of 1.4%.
Will the increase in the CSG appear in the final version of the Budget?
The fact remains that the amendment raising the rate of the CSG (and therefore the flat tax), if it was indeed adopted in the National Assembly, will perhaps not appear in the final version of the PLFSS which will be adopted. This would require senators and deputies to agree on this increase. In the absence of agreement between the two houses of Parliament, the government could try to pass the budget by ordinance, but in this case, “it is the original, unamended text that is voted on. However, this increase was integrated by way of an amendment, it would not be applied”recalls Nicolo Acquari. Finally, like last year, a special law could be promulgated, but with this option, the 2025 budget would be renewed for 2026, without an increase in the CSG as well.
