Although income tax has been deducted at source since January 2019 (Editor’s note: each month, a percentage of salaries is deducted to pay part of the income tax owed by the employee), it is still necessary to complete a tax return to calculate the final amount of the amount owed to the tax authorities. If it does not correspond to the tax paid, you must either pay an additional amount or be reimbursed in the event of an overpayment.
For example, the declaration made in the spring until June 4, 2026 depending on your department of residence, allows you to calculate the tax due according to your income earned in 2025. If the deductions made at source the previous year correspond to the amount of your tax calculated at the end of the declaration, your income tax is paid. So much the better because you don’t have to do any other additional steps.
Income taxes: why do I have to pay extra?
If the amount of your tax calculated from your declaration is higher than the total amount of deductions made during the previous year, you still have one supplement to pay. How can these differences be explained? There are several possibilities. If your income increased during the year but you have not requested to change your withholding tax rate, you will be affected. Afterwards, if you received too high a deposit of reductions or tax credits. Finally, the additional (balance) tax payable is indicated on your tax notice. Please note that it is possible to request a payment deadline in case of difficulties to pay this supplement: “ Do not hesitate to contact the personal tax service to request an installment, greater than 4 months and often authorized. », Specifies Aurélia Barraud, national secretary of Solidaire finances publics.
For example, in 2025, you paid 150 euros per month in withholding tax, for an annual total of 1,800 euros. When you file your declaration in spring 2026, the tax calculated is 2,100 euros. There are therefore 300 euros left to pay. How can I pay this difference? If the amount does not exceed 300 euros, it will be taken directly from your bank account in September 2026. If it is greater than 300 euros, it will be taken in several installments between September and December 2026. Please note, you must not forget that you continue to pay your withholding tax for the current year, in addition to the additional tax.
Income taxes: what to do if you overpay?
Otherwise, if the tax calculated from your declaration is lower than the total deductions made the previous year, this means that you have paid too much income tax. Therefore, the tax authorities must reimburse you for this overpayment. How to explain it? In the event of a drop in income during the year without change in the deduction rate. Or, if there are any remaining tax reductions or credits from the previous year (already indicated on your tax notice).
Starting from the same example cited above with 150 euros per month of withholding tax for an annual amount of 1,800 euros, this time your tax calculated from your declaration is 1,600 euros. You will be entitled to a refund of 200 euros which will take the form of a transfer to your bank account during the summer. Knowing that you continue to pay your withholding tax for the current year.
An automatically updated rate
Did you know? According to your tax return made in the spring, your withdrawal rate is done automatically in September following but you have the possibility to change it first: “ At the end of your tax return, on the last tree, you can request that your rate change immediatelyreveals Aurélia Barraud. The information is submitted to the third party collector within 30 days. This is the whole point of this withholding tax rate, being able to modulate it to better control it. “.
