Individuals and unincorporated entities that regularly conduct business using an assumed name (often called a DBA ) must file an assumed name certificate with the county clerk in each county in which business premises are maintained. If corporations, limited liability companies or limited partnerships (entities created by filing with the secretary of state) do business with a name that is different from the name in the organizational documents, they must file assumed name certificates in the county or counties where the registered office and the principal office are located, and must also file with the secretary of state.