@giovannag1 That is not enough information. Was the income reported on a W-2? Was tax withheld? It would depend on how much tax the employer withheld--prepare a tax return to see.
Or if the income was for self-employment---or income reported on a 1099Misc then there would be self-employment tax and ordinary income tax owed.
Try using Free File to prepare a tax return. An eighteen year old is likely someone else's dependent, so that must be indicated in My Info.
Try Free File:
You qualify if your income was $36,000 or less, or $69,000 or less if active duty military, or if you qualify for Earned Income Credit
https://ttlc.intuit.com/questions/1900583-what-is-turbotax-free-file-program
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
