Can I claim my 23 year old child who lived with us and was supported 100% by us for entire year. He did not work due to a disability.

You can claim him as dependent as long as he meets the following requirements:

Qualifying child:

• They're related to you.
• They aren't claimed as a dependent by someone else.
• They're a US 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).
• There's 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.

Or, 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 US 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 $5,050 in 2024.
• You provided more than half of their financial support.