If the single-member LLC has not filed an election with the IRS to be treated as a C corp or S corp for income tax purposes, then the LLC is disregarded for income tax purposes. It's just you. The business income is your personal income. You do not file a separate tax return for the business. Your business income and expenses are reported on Schedule C, included in your personal tax return, and the net business income (profit) is added to your personal income.
If your net business income is more than $432, your tax return will also include self-employment tax on your net business income. The nominal rate for self-employment tax is 14.13% (15.3% tax on 92.35% of your self-employment income). The effective rate will vary from 11.52% to 14.13% depending on your total taxable income.
