In the US a sole proprietorship is a business. A sole proprietorship is the most common form of business in the United States. Sole Proprietorships do not require LLC or C corporation filings. Often but not always they require a business license. If one does not have business partners and is running a software company, the sole proprietorship is the most sensible form. Note that LLCs do not protect the actual developer from liability from his errors, they only protect the partners from liability from errors they themselves did not personally create. To protect oneself from ones own errors, businesses should acquire E&O insurance. Software development businesses that do not have E&O insurance are putting themselves at risk.