A California “foreign LLC” refers to a business that has been created in a U.S. state other than California. If you plan to do business in California, the business needs to be registered in the state. In this context, “foreign” doesn't mean another country, but another state within the U.S. A business that was organized in the state where it does business is referred to as a “domestic LLC”.
California's LLC Act requires foreign LLCs to register with the state of California – if they are transacting any type of business within the state. Although this is not specifically defined, determining when state sales taxes must be collected helps to answer this question. Simply put, when a business has a physical presence in the state, it must collect sales tax on its sales to residents of that state.