If you are operating your eBay business as a sole proprietorship or partnership, you can convert to an LLC with no change to your income tax treatment and filing requirements. In other words, the owner (or owners) of an LLC files taxes in the same way as a sole proprietorship or partnership.
If your eBay business is a partnership, you and your partners must agree in writing to terminate the partnership and convert to an LLC. You may have to complete additional paperwork to legally terminate your partnership when you convert it to an LLC — for example, publish a notice of dissolution in a newspaper. Check with your secretary of state. Since your new LLC assumes the debts of your prior partnership, you should seek the advice of your accountant or tax consultant before making the conversion.