You are a business in the IRS eyes.
You do not have to carry on regular full-time business activities to be considered self-employed. You will notice the amount you were paid probably appears in box 7 of your 1099-MISC. This is non-employee compensation. You were contracted to do a job, not employed to do a job. You will need to file a Schedule C for Business Income and Expenses and pay Self-Employment tax on this income.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"