Income Tax - Income and Attachment of a Major Child

Verified 15 April 2026 - Public Service / (Prime Minister)

How to report the income of a young person who has reached the age of 18 on 1er January 2025? In principle, the young adult makes his own statement. However, he may, under certain conditions, remain liable to his parents' taxes. Whether you are the parents or the young person concerned, we tell you what you need to know for the 2026 income tax return for 2025.

What applies to you ?

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You are the parents

The rules differ depending on your child's situation:

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Your adult child is single

You have the choice between 2 solutions:

  • Attach it to your tax return
  • Let him file his own tax return.

If you're separated, only one of you 2 can attach his statement.

Attaching your adult child to your declaration allows you to benefit from a increase in your number of shares.

But if the young man makes his own statement, you can give him paying child support, deductible of your taxable income.

The choice is made of one common agreement.

Depending on your situation, one of the choices may be more advantageous for tax purposes.

To make your choice, you can do a simulation of the calculation with the following online service:

Estimate the amount of your 2025 income tax (2026 return)

Your adult child is attached to your return

The period depends on your child's age and situation:

Your child is under 21 years old

Your child can be attached to your tax home if he is under 21 at 1er January 2025.

So you can't attach it if it was born before 1er January 2004.

The attachment of your adult child allows you to benefit from a increase in the number of shares from family quotient.

Your attached child has no personal tax return to be subscribed.

You must do the following:

  • Add to your income those received by your adult child
  • Maintain attach request (attestation on honor) of your child to present it in case of request from the administration.

If you pay a child support to your adult child, you cannot deduct it from your taxable income.

If he or she does not live with you, you must indicate his or her address in your return.

Your child is over 21 years old

The period depends on your child's situation and age:

Your adult child is a student

If your child is a student, he or she can be attached to your tax home if he is old under 25 years of age at 1er January 2025.

So you can't attach it if it was born before 1er January 2000.

The attachment of your adult child allows you to benefit from a increase in the number of shares from family quotient.

Your attached child has no personal tax return to be subscribed.

You must do the following:

  • Add to your income those received by your adult child
  • Maintain attach request (attestation on honor) of your child to present it in case of request from the administration.

If you pay a child support to your adult child, you cannot deduct it from your taxable income.

If he or she does not live with you, you must indicate his or her address in your return.

Your adult child is disabled

If your child is disabled, it shall be considered to be the tax liability of your tax home, regardless of age.

Your child is considered disabled if, because of his disability, he is unable to provide for himself.

This is the case whether or not he holds one of the following documents:

Please note

If your child has a disability MIF (or a disability card), you are entitled to a markup additional of your family quotient.

Your child of legal age in your care allows you to increase in the number of shares from family quotient.

Your child has no personal tax return to be subscribed.

You must add to your income those received by your adult child.

If you pay a child support to your adult child, you cannot deduct it from your taxable income.

Other case

You cannot attach your adult child to your return.

He has to file his own tax return.

If you pay him a child support, you you can deduct it of your taxable income.

Your adult child makes his own declaration

If your adult child is not attached to your tax home, he must file your own tax return.

If you pay child support, you can deduct it from your incomewithin certain limits.

Your adult child is married, entered into a civil partnership or responsible for the family

You have the choice between 2 solutions:

  • Attach him/her to your tax return (entered into a civil partnership or married) and/or dependent child
  • Let him file his own tax return.

The choice is made of one common agreement.

Depending on your situation, one of the choices may be more advantageous for tax purposes.

To make your choice, you can do a simulation of the calculation with the following online service:

Estimate the amount of your 2025 income tax (2026 return)

Your adult child is counted as a dependant on your return

The period depends on your child's age and situation:

Your child is under 21 years old

Your adult child can be attached to your tax home if he is under 21 to 1er January 2025.

So you can't attach it if it was born before 1er January 2004.

Please note

If your child is married or entered into a civil partnership, it is enough for one of the spouses to fulfill the condition.

The attachment of your adult child who is married, entered into a civil partnership or in charge of the family does not allow you to benefit from an increase in your family quotient.

It allows you to benefit from a abatement on your income from €6,855 per person attached.

Example :

If you reunite your married child and parent of a child, you are entitled to a €20,565.

Your child who is married or entered into a civil partnership has no personal tax return to be subscribed.

You must do the following:

  • Enter on your return the number of children of full age attached to your household
  • Add to your income those received by your child(ren)
  • Maintain attach request (attestation on honor) of your child to present it in case of request from the administration.

If you pay a child support to your child, you can't deduct it of your taxable income.

If your adult child does not live with you, you must indicate his address in your declaration.

Warning  

Your child who is married or entered into a civil partnership can request that he be attached to your home or to the home of the in-laws, but not to the 2.

Your child is over 21 years old

The period depends on your child's situation and age:

Your child is a student

If your child is a student, he or she can be attached to your tax home if he is under 25 to 1er January 2025.

So you can't attach it if it was born before 1er January 2000.

Please note

If your child is married or entered into a civil partnership, it is enough for one of the spouses to fulfill the condition.

The attachment of your adult child who is married, entered into a civil partnership or in charge of the family does not allow you to benefit from an increase in your family quotient.

It allows you to benefit from a abatement on your income from €6,855 per person attached.

Example :

If you reunite your married child and parent of a child, you are entitled to a €20,565.

Your child who is married or entered into a civil partnership has no personal tax return to be subscribed.

You must do the following:

  • Enter on your return the number of children of full age attached to your household
  • Add to your income those received by your child(ren)
  • Maintain attach request (attestation on honor) of your child to present it in case of request from the administration.

If you pay a child support to your child, you can't deduct it of your taxable income.

If your adult child does not live with you, you must indicate his address in your declaration.

Warning  

Your child who is married or entered into a civil partnership can request that he be attached to your home or to the home of the in-laws, but not to the 2.

Your child is disabled

If your child is disabled, it can be attached to your tax home regardless of age.

Your child is considered disabled if, because of his disability, he is unable to provide for himself.

This is the case whether or not he holds one of the following documents:

If your child is disabled, he or she can be attached to your tax home regardless of age.

Please note

If your child is married or entered into a civil partnership, it is enough for one of the spouses to meet the disability condition.

The attachment of your adult child who is married, entered into a civil partnership or in charge of the family does not allow you to benefit from an increase in your family quotient.

It allows you to benefit from a abatement on your income from €6,855 per person attached.

Example :

If you reunite your married child and parent of a child, you are entitled to a €20,565.

Your child who is married or entered into a civil partnership has no personal tax return to be subscribed.

You must do the following:

  • Enter on your return the number of children of full age attached to your household
  • Add to your income those received by your child(ren)
  • Maintain attach request (attestation on honor) of your child to present it in case of request from the administration.

If you pay a child support to your child, you can't deduct it of your taxable income.

If your adult child does not live with you, you must indicate his address in your declaration.

Warning  

Your child who is married or entered into a civil partnership can request that he be attached to your home or to the home of the in-laws, but not to the 2.

Other case

You cannot attach your adult child to your return.

Your adult child must file his or her own tax return.

If you pay a child support to your child, you you can deduct it of your taxable income.

You child of full age makes his own statement

If your adult child is not attached to your tax home, he must file your own tax return.

If you pay child support, you can deduct it from your incomewithin certain limits.

You're a young adult

The rules differ depending on your situation.

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You're single

You have the choice between 2 solutions:

  • Attach yourself to your parents' tax return
  • Make your own tax return.

If your parents are separated, you can attach only to the declaration of one of the 2.

Attaching yourself to your parents' declaration allows them to benefit from a increase in their number of shares.

But if you make your own declaration, they can declare deduct child support from their income they'll pay you. You have to declare it.

The choice is made of one by mutual agreement.

Depending on your situation, one of the choices may be more advantageous for tax purposes.

To make your choice, you can do a simulation of the calculation with the following online service:

Estimate the amount of your 2025 income tax (2026 return)

You are attached to your parents' declaration

The rules depend on your age and situation:

You are under 21 years old

You can be attached to tax home of your parents if you are under 21 at 1er January 2025.

So you can't be attached if you were born before 1er January 2004.

Your parents benefit from a increase in their number of shares from family quotient.

You don't have a personal tax return to take out.

Your income must be included on your parents' income tax return.

If you do not live with your parents, they must include your address in their return.

You are over 21 years old

The rules depend on your situation and your age:

You are a student

If you are a student, you can be attached to the tax home of your parents if you are elderly under 25 years of age at 1er January 2025.

So you can't be attached if you were born before 1er January 2000.

Your parents benefit from a increase in their number of shares from family quotient.

You don't have a personal tax return to take out.

Your income must be included on your parents' income tax return.

If you do not live with your parents, they must include your address in their return.

You are disabled

If you have a disability, you can remain fiscally responsible for the tax home of your parents, whatever your age.

You are considered disabled (infirm) if, because of your disability, it is you can't support yourself.

This is the case whether or not you have one of the following documents:

Your parents benefit from a increase in their number of shares from family quotient.

Please note

If you have a disability MIF (or a disability card), your parents are entitled to markup additional of their family quotient.

You don't have a personal tax return to take out.

Your income must be included on your parents' income tax return.

Other case

You cannot be linked to your parents' statement.

You have to file your own tax return.

If your parents pay you a child support, they can deduct it from their income within certain limits.

In this case, you must declare it.

You make your own statement

If you are not attached to yours tax home of your parents, you must file your own tax return.

If your parents pay you a child support, they can deduct it from their income within certain limits.

In this case, you must declare it.

You are married, entered into a civil partnership or responsible for your family

You have the choice between the 2 solutions:

  • Attach yourself to your parent's income tax return with your spouse (married or entered into a civil partnership) and/or dependent child
  • Make your own tax return.

The choice is made of one common agreement.

Depending on your situation, one of the choices may be more advantageous for tax purposes.

To make your choice, you can do a simulation of the calculation with the following online service:

Estimate the amount of your 2025 income tax (2026 return)

You're counting on your parents' return

The rules depend on your age and situation:

You are under 21 years old

You may, by mutual agreement, be attached to the tax home of your parents or in-laws if you are under 21 to 1er January 2025.

So you can't be attached if you were born before 1er January 2004.

If you are married or entered into a civil partnership, it is sufficient that you or your partner meet the age requirement.

Warning  

You can ask for your connection either to your parents' home or to the home of his in-laws, but not to the 2.

Your attachment to your parents' (or in-laws') tax household allows them to benefit from a abatement on their income from €6,855 per person attached.

You have no personal tax return to be subscribed.

Your parents (or in-laws) must include your income and that of your entered into a civil partnership or married spouse on their return.

If you do not live with your parents (or in-laws), they must include your address in their return.

You are over 21 years old

The rules depend on your situation and your age:

You are a student

If you are a student, you can be attached to the tax home of your parents or in-laws if you are under 25 to 1er January 2025.

So you can't be attached if you were born before 1er January 2000.

If you are married or entered into a civil partnership, it is sufficient that you or your partner meet the age requirement.

Warning  

You can request your connection either to your parents' home or to your in-laws' home, but not to the 2.

Your attachment to your parents' (or in-laws') tax household allows them to benefit from a abatement on their income from €6,855 per person attached.

You have no personal tax return to be subscribed.

Your parents (or in-laws) must include your income and that of your entered into a civil partnership or married spouse on their return.

If you do not live with your parents (or in-laws), they must include your address in their return.

You are disabled

If you are disabled, you can be attached to the tax home of your parents whatever your age.

You are considered disabled (infirm) if, because of your disability, it is you can't support yourself.

This is the case whether or not you have one of the following documents:

If you are married or entered into a civil partnership, it is sufficient that you or your partner meet the disability condition.

Warning  

You can request your connection either to your parents' home or to your in-laws' home, but not to the 2.

Your attachment to your parents' (or in-laws') tax household allows them to benefit from a abatement on their income from €6,855 per person attached.

You have no personal tax return to be subscribed.

Your parents (or in-laws) must include your income and that of your entered into a civil partnership or married spouse on their return.

If you do not live with your parents (or in-laws), they must include your address in their return.

Other case

You cannot be linked to your parents' statement.

You have to file your own tax return.

If your parents pay you a child support, you must declare it.

If your parents pay you a child support, they can deduct it from their income within certain limits.

In this case, you must declare it.

You make your own statement

If you are not attached to yours tax home of your parents, you must file your own tax return.

If your parents pay you a child support, they can deduct it from their income within certain limits.

In this case, you must declare it.

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