MY DEPENDENT HAD A JOB
If your dependent has a W-2 for his after-school job, summer job, etc. you do not include the information on your own return. You can still claim your child as a dependent on your own return. He/she can file his own return for a refund of some of his withheld wages (he won’t get back anything for Social Security or Medicare), but MUST indicate on it that he can be claimed as a dependent on someone else’s return. (Supervise this closely or prepare it for him!)
If your dependent’s earnings were over $400 and were reported on a 1099Misc or 1099NEC then he must file a return and pay self-employment tax for Social Security and Medicare.
You might also want to use free software from the IRS Free File versions:
https://apps.irs.gov/app/freeFile/
Your son would have to file a return if he had net earnings from self-employment of at least $400, as Tax Champ xmasbaby0 advises. Additionally, if you live in a state with an income tax, the filing threshold may be lower.
See Line 3 in Table 3 of Other Situations.
Your son can claim expenses against his income to reduce any tax due.
See “The ultimate guide to tax deductions for the self-employed.”
He can also contribute to an individual retirement arrangement (IRA) assuming you can find a bank or brokerage that will allow him to open an account.