A Sole Proprietorship (including a Single Member LLC that has NOT made an election to be taxed as a corporation) does not need to file any tax returns until your personal tax return is due in April 2018. However, you probably should be paying Estimated Taxes in the meanwhile.
<a rel="nofollow" target="_blank" href="
https://www.irs.gov/businesses/small-businesses-self-employed/estimated-taxes">https://www.irs.gov/b...>
If the LLC DID file the form to be taxed as a corporation, the 'short answer' is to see a tax professional As Soon As Possible. It needs to file quarterly employer forms (you are required to be on payroll), and if you don't do things correctly, it can easily cost you thousands of 'extra' dollars for doing things wrong. In my opinion, every new corporate owner (including an LLC taxed as a corporation) should REALLY go to a tax professional BEFORE the business starts, and for AT LEAST the first year.
