You need to formally close your corporation.
You must file Form 966, Corporate Dissolution or Liquidation, if you adopt a resolution or plan to dissolve the corporation or liquidate any of its stock.
You must also file your corporation’s final income tax return. Remember to check the “final return” box, which is near the top of the front page of the return, below the name and address.
For a C corporation you must:
For an S corporation you must:
Regardless of the type of corporation, you may also need to file these forms when you file your Form 1120 or 1120-S:
Please see this link from the IRS regarding closing your business.
https://www.irs.gov/businesses/small-businesses-self-employed/closing-a-business
Once that is done, you can begin your Schedule C business.
You will need to file Form 8832 Entity Classification Election to change to t a single-member disregarded LLC. Generally, an election specifying an LLC’s classification cannot take effect more than 75 days prior to the date the election is filed, nor can it take effect later than 12 months after the date the election is filed. An LLC may be eligible for late election relief in certain circumstances.
You would indicate on line 6(c) part 1 of Form 8832 that you are electing to be treated as a disregarded separate entity.
See additional guidance in the IRS link below. Click on Form 8832 Entity Classification Election once you are on the website.
Limited Liability Company (LLC)