If you had a W-2 for $2739, you would not have to file because that is less than the $12,200 filing threshold.
But, income, other than W-2 wages is treated differently.
If you are paid off the books, in cash, you are not an "employee". You are a "contract employee" or independent contractor. The IRS considers undocumented cash income (no W-2 or 1099-MISC), for work performed, to be self employment income. Enter at "Business Income & Expenses" and TurboTax (TT) will complete Schedule C or C-EZ for you and allow you to deduct any expenses associated with this income. You'll also have to pay self employment tax (social security & medicare tax) on any "profits"greater than $400.
