My son claimed himself as a dependant on his taxes, but we did not claim him. he filed. what should we do?

Your post is confusing.....it is not really clear how your son answered the question in My Info---first you say he "claimed himself" then you say he "called himself a dependent."   Please look at the top of  his Form 1040 and see if the box for being claimed as a dependent is checked or not checked.

The rule is if he CAN be claimed as a dependent on someone else's tax return he must say so on his own return, even if no one actually claims him.   So....CAN he be claimed as either a qualified child or qualified relative?  

IRS interview to help determine who can be claimed:

https://www.irs.gov/help/ita/who-can-i-claim-as-a-dependent

https://ttlc.intuit.com/questions/3113432-who-can-i-claim-as-my-dependent  

You have not mentioned your son's age, whether he was a full-time student in 2022, or how much he earned in 2022.   If he said on his return that he could be claimed as a dependent, then his standard deduction was affected--if he earned more than $12,950, so he may have had more tax liability than he would have if he said he cannot be claimed.  

WHO CAN I CLAIM AS A DEPENDENT?

You can claim a child, relative, friend, or fiancé (etc.) as a dependent on your 2022 taxes as long as they meet the following requirements:

Qualifying child

• They're related to you.
• They aren't claimed as a dependent by someone else.
• They're a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They're under the age of 19 (or 24 for full-time students).
• No age limit for permanently and totally disabled children.
• They lived with you for more than half the year (exceptions apply).
• They didn't provide more than half of their own support for the year.

Qualifying relative

• They don't have to be related to you (despite the name).
• They aren't claimed as a dependent by someone else.
• They're a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They lived with you the entire year (exceptions apply).
• They made less than $4,400 in 2022.
• You provided more than half of their financial support.

The standard deduction amount for an individual who may be claimed as a dependent by another taxpayer cannot exceed the greater of $1,100 or the sum of $400 and the individual’s earned income (not to exceed the regular standard deduction amount).

Your standard deduction lowers your taxable income.  It is not a refund.  You will see your standard or itemized deduction amount on line 12 of your 2022 Form 1040.

2022 STANDARD DEDUCTION AMOUNTS

SINGLE $12,950  (65 or older + $1750)

MARRIED FILING SEPARATELY $12,950  (65 or older + $1750)

MARRIED FILING JOINTLY $25,900  (65 or older + $1400 per spouse)

HEAD OF HOUSEHOLD  $19,400  (65 or older +$1750)

Legally Blind + $1750

He may need to amend to change the way he answered the question in My Info as to whether he can be claimed.

See this TurboTax support FAQ for amending a tax return - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-change-correct-return-a...

If your son claimed himself as a dependent on his tax return, then he should amend as Tax Champ xmasbaby0 said.

It may or may not flag with the IRS since you are not claiming him as your dependent. 

If you do hear from IRS it probably will not create any negative tax changes. You did not claim your son so there’s nothing to adjust on your return. On his return, if anything, he may not have claimed a credit he was entitled to, such as education expenses, by listing himself as a dependent.

When he amends, he can add anything that was missed.