18 year old earnings

For the federal return, he would not be REQUIRED to file- but if he had withholding, he can get that refunded if he files.  You would have to check your state requirements.  

Q. Grandson in high school. Made $1800 at a part time job. Does he have to file?

A. No, if the job was a regular W-2 reported income job. 

 If the dependent child is under age 19 (or under 24 if a full time student), he or she must file a tax return for 2024 if he had any of the following:

1.  Total income (wages, salaries, taxable scholarship etc.) of more than $14,600 ($13,850 for2023).
2.  Unearned income (interest, dividends, capital gains, unemployment, taxable portion of 529 distribution) of more than $1300 ($1250 for 2023). 
3. Unearned income over $450 and gross income of more than $1300.
4.  Household employee income (e.g. baby sitting, lawn mowing) over $2600 ($14,600 if under age 18)
5.  Other self employment income over $432, including money on a form 1099-NEC

W2 no. Otherwise,  best to check due to the variety of scenarios - even scholarship can sometimes be income. You can take a quick quiz, Filing requirement - Do I need to file a tax return?

Each state is very different for taxable income. You can reply with the state and we will be glad to check for you.