Tax 2026: This Common Mistake Divorced Parents Make Can Cost You the Tax Deduction Related to Your Child Support

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Tax 2026: This Common Mistake Divorced Parents Make Can Cost You the Tax Deduction Related to Your Child Support

Created on 02/04/2026 at 07:06, by Joséphine de Rubercy

Declaring child support on your 2026 tax return can open the door to a valuable tax deduction… provided you don’t make a fatal mistake. Which boxes to fill out (6EL, 6GU, 6DD…)? How to avoid pitfalls? Here’s everything you need to know to not lose out.

The tax declaration season will officially open on Thursday, April 9, 2026. Each taxpayer will be invited to report their 2025 income and to carefully consider the various deductible expenses. Thanks to certain tax reductions, it is possible to significantly lighten your taxable income... as long as you are vigilant. Because beware: a wrong box checked, a missing supporting document, or an imprecise declaration can cost you dearly. Among the expenses that can be deducted from your return is child support, which refers to the amount paid by one parent to the other after a separation or divorce to contribute to the costs related to the maintenance and education of the child.

While tax deductions are allowed in many cases (support paid for a minor child, assistance to a parent in need…), it is essential to follow the exact procedure set by the administration. Every detail counts: capped amounts, documents to provide, specific boxes to fill out... And above all, there is a common mistake made by many parents that can cost you any tax advantage. Here’s how to avoid the trap and optimize your 2026 tax return without stress.

Taxes 2026: How to Properly Declare Child Support Paid?

When you pay child support, it can be deducted from your taxable income, but beware: you must fill out the correct boxes and meet certain specific conditions. First, the amount paid must correspond to a genuine obligation of support as stipulated by the Civil Code: support for children, parents, or even grandparents if necessary. For a minor child, the deduction is possible if you do not have primary or shared custody, by declaring the amounts in boxes 6GU (decision made after 2006) or 6GP (decision made before).

For an adult child not attached for tax purposes, the support is deductible up to €6,794 per year (or €8,079 if married or in a civil partnership). You must indicate the amounts paid in boxes 6EL or 6EM. "It is crucial to keep all proof of payment, including bank transfers and invoices paid on their behalf," emphasizes the DGFIP. In case of doubt, the tax authorities may request supporting documents for up to three years.

Note: For assistance to parents, if their income is below €12,411.36 (single person) or €19,268.76 (couple), you can also deduct the amounts paid, without a ceiling but with precise supporting documents.

How to Declare Child Support Received?

Conversely, if you receive child support, you must add it to your taxable income. More specifically, if you are a parent receiving support for a minor or attached child, you must report it in box 1AO or 1BO. If the support is paid directly to an adult child, it should be declared in 1CO or 1DO. Note that you will automatically benefit from a 10% deduction on these reported amounts. The administration considers that part of this sum is used for unavoidable expenses.

But beware: failing to declare received child support is a serious offense that can lead to a tax adjustment, with a penalty that can rise up to 40% of the initially owed amount. As the DGFIP reminds us, "an omitted income is an undervalued income, and thus a tax offense". The stakes are to declare everything accurately, using the correct boxes to avoid any errors or unpleasant audits.

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What is the Number One Mistake with Child Support in the Tax Declaration?

Every year, thousands of taxpayers make the same mistake. Yet it is simple to avoid: checking the wrong box when entering the amount of child support. For support paid, you must use box 6EL if the child is an adult. And box 6GU if they are a minor. It also happens that box 6DD is mistakenly filled out. While it is intended for other types of deductions than child support. For their part, recipients of the support must report it in boxes 1AO to 1DO. Another common mistake: not prorating the deduction of the flat amount of €4,039 if the child or parent was only housed for a few months with them. For each incomplete month, the deduction must be adjusted!

Finally, the last common mistake parents make is to declare child support for a child in shared custody. And this is strictly prohibited! In the case of shared custody, each parent can share the family quotient. But no child support paid can be deducted. Even if you pay an amount to your ex-spouse to balance expenses. You cannot subtract it from your taxable income in any case. The result: any deduction made in error is systematically canceled by the tax administration, with additional penalties and late interest.

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What Are the Best Practices to Avoid Mistakes and Maximize Deductions?

To fully benefit from the tax deduction, a few simple reflexes can save you a lot of trouble. First, standardize bank transfers for all child support payments. They provide solid proof in case of an audit. Next, keep all supporting documents safe: court decisions, sworn statements, rent receipts, medical invoices, etc. When filing your online declaration, pay particular attention to boxes 6EL, 6GU, 6DD... and take your time.

Check that you do not combine tax attachment and support deduction for the same adult child: this is prohibited. In the case of a parent being housed, do not forget to check their income level to ensure that the child support is deductible. Finally, if you help a married adult child, do not forget to adjust the deduction ceiling to €8,079 or €13,588 depending on their family situation. In short, every tax situation is unique, and it is better to anticipate than to correct afterwards. An error-free declaration is the key to avoiding fines and adjustments.