| 18 Under Limited | Private company limited by shares | Live |
| UNDER10 Limited | | Live |
| Under20 Limited | | Live |
| Under9 Limited | Private company limited by shares | Live |
| Underbelly Asia Limited | Private company limited by shares | Live |
| Underbrow Eyewear Limited | Private company limited by shares | Live |
| UNDERCLIFF LIMITED | Private company limited by shares | Dissolved |
| HK SHEYOUNG UNDERCLOTHES LIMITED | Private company limited by shares | Dissolved |
| Undercover Asia Limited | Private company limited by shares | Live |
| UNDERCOVER MOTHER LIMITED | Private company limited by shares | Dissolved |
| Undercover Nerds Limited | Private company limited by shares | Live |
| UNDERCROFT LIMITED | Private company limited by shares | Dissolved |
| UNDERCURRENT RISK MANAGEMENT LIMITED | Private company limited by shares | Live |
| UNDERCUT GROUP LIMITED | Private company limited by shares | Live |
| Underdavinci Limited | Private company limited by shares | Live |
| Underdog Can Consultancy Limited | Private company limited by shares | Live |
| Underdog Fitness Limited | | Live |
| UNDERDOG RESTAURANTS LIMITED | Private company limited by shares | Live |
| Underdog Solutions Limited | Private company limited by shares | Live |
| Underdogs Limited | Private company limited by shares | Live |
| Under-Earth Limited | | Live |
| SIMPLY UNDERFLOOR HEATING LIMITED | Private company limited by shares | Live |
| PARINA UNDER-GARMENT FACTORY LIMITED | Private company limited by shares | Dissolved |
| TAK FRANCE UNDERGARMENT LIMITED | Private company limited by shares | Dissolved |
| HK GEIYU FASHIONABLE UNDERGARMENT LIMITED | Private company limited by shares | Dissolved |
| REPUBLIC UNDERGARMENT COMPANY, LIMITED | Private company limited by shares | Dissolved |
| TETLY UNDERGARMENT COMPANY LIMITED | Private company limited by shares | Live |
| UNDERGRAVITY PRODUCTION LIMITED | Private company limited by shares | Live |
| UNDERGROUND LIMITED | Private company limited by shares | Dissolved |
| GL UNDERGROUND LIMITED | Private company limited by shares | Live |
| UNDERGROUND LIMITED -THE- | Private company limited by shares | Live |
| Underground HK Limited -The- | Private company limited by shares | Live |
| Underground Chef Limited -The- | Private company limited by shares | Live |
| CHOI'S UNDERGROUND UTILITY DETECTION CONSULTANT CO. LIMITED | Private company limited by shares | Dissolved |
| GLOBAL CITY UNDERGROUND SPACE INVESTIGATIVE LIMITED | Private company limited by shares | Live |
| UNDERGROUND CLASSICS LIMITED | Private company limited by shares | Live |
| UNDERGROUND RESEARCH TECHNOLOGY CO., LIMITED | Private company limited by shares | Dissolved |
| HCC Underground Pipeline Consultant Limited | Private company limited by shares | Live |
| Creative Underground Limited | Private company limited by shares | Live |
| Underground Creative Limited | Private company limited by shares | Live |
| Underground Development Limited | Private company limited by shares | Dissolved |
| ESI Tai He Underground Space Development Limited | Private company limited by shares | Live |
| D-tech underground management Limited | Private company limited by shares | Live |
| UNDERGROUND EXPERTISE LIMITED | Private company limited by shares | Live |
| UNDERGROUND MATERIALS SUPPLY H.K. LIMITED | Private company limited by shares | Dissolved |
| UNDERGROUND TOYS (H.K.) LIMITED | Private company limited by shares | Live |
| Underground Fun (HK) Trading Limited | Private company limited by shares | Live |
| HONG KONG UNDERGROUND CABLE ENGINEERING LIMITED | Private company limited by shares | Dissolved |
| HONG KONG UNDERGROUND ENGINEERING LIMITED | Private company limited by shares | Dissolved |
| TONGJI UNDERGROUND SPACE RESEARCH INSTITUTE LIMITED | Private company limited by shares | Live |
| UNDERGROUND INTERNATIONAL LIMITED | Private company limited by shares | Dissolved |
| UNDERGROUND SOLUTIONS INTERNATIONAL LIMITED | Private company limited by shares | Dissolved |
| PATRICK YUEN UNDERGROUND DETECTION COMPANY LIMITED | Private company limited by shares | Live |
| Underground Projects Limited | Private company limited by shares | Live |
| Solar Underground Limited | Private company limited by shares | Dissolved |
| UNDERHEAVENCRYPTO LIMITED | | Live |
| UNDERHILL ASSOCIATES LIMITED | Private company limited by shares | Live |
| UNDERHILL ENTERPRISES (HONG KONG) LIMITED | Private company limited by shares | Dissolved |
| SO UNDERHORSE FITNESS LIMITED | Private company limited by shares | Live |
| UNDERLAY FACTORY LIMITED | Private company limited by shares | Live |
| UNDERLINE OFFICE COMPANY LIMITED | Private company limited by shares | Dissolved |
| UNDERLINES (ASIA) MFG CO. LIMITED | Private company limited by shares | Dissolved |
| Underlyne Limited | Private company limited by shares | Live |
| Underpin Company Limited | Private company limited by shares | Live |
| Underrated Limited | | Live |
| Underscore Entertainment Limited | Private company limited by shares | Live |
| I UNDERSTAND LIMITED | Private company limited by shares | Live |
| UNDERSTAR LIMITED | Private company limited by shares | Dissolved |
| UNDERSTATED LIMITED | 私人股份有限公司 | 仍註冊 |
| UNDERSTOOD FAST TIME FINANCIAL ICP LIMITED | Private company limited by shares | Dissolved |
| Undersun Incorporated Limited | Private company limited by shares | Live |
| EDEN UNDERTAKER LIMITED | Private company limited by shares | Live |
| C.L UNDERTAKERS LIMITED | Private company limited by shares | Live |
| CHINA CHAOJING CULTURAL UNDERTAKING CO., LIMITED | Private company limited by shares | Live |
| Topken Cultural Undertaking Limited | Private company limited by shares | Dissolved |
| HK MUYANG GREAT UNDERTAKING (INT'L) FASHION LIMITED | Private company limited by shares | Dissolved |
| GREAT UNDERTAKING INFORMATION TECHNOLOGY LIMITED | Private company limited by shares | Live |
| UNDERTAKING JOINT INDUSTRIAL LIMITED | Private company limited by shares | Live |
| Educational Undertakings International Group Limited | Private company limited by shares | Live |
| UNDERTHEPILLOW LIMITED | Private company limited by shares | Live |
| UNDERTOW LIMITED | | Live |
| UNDERVERSE LIMITED | Private company limited by shares | Live |
| 70s Babyware N underware Trading Limited | Private company limited by shares | Dissolved |
| UNDERWATER ADVENTURE BOAT CO. LIMITED | Private company limited by shares | Live |
| Shenzhou Underwater Engineering Technical Advisory Services Limited | Private company limited by shares | Live |
| UNDERWATER WORLD CHINA LIMITED | Private company limited by shares | Dissolved |
| Sea Dweller Underwater Academy Limited | Private company limited by shares | Live |
| Ningbo Far-East Underwater Engineering Co., Limited | Private company limited by shares | Dissolved |
| DALI Underwater Engineering HK Limited | | Live |
| POTENT UNDERWATER ENGINEERING LIMITED | Private company limited by shares | Live |
| HONG KONG UNDERWATER ASSOCIATION LIMITED | Company limited by guarantee | Live |
| HONG KONG CHINA UNDERWATER ARCHAEOLOGICAL EXPEDITION SOCIETY LIMITED | Private company limited by shares | Dissolved |
| Hong Kong Underwater World Mixed Juice Seafood (China) Catering Group Co., Limited | | Live |
| HONG KONG UNDERWATER RESORT INTERNATIONAL GROUP LIMITED | Private company limited by shares | Live |
| Hong Kong Underwater Performing Arts Association Limited | | Live |
| China Hong Kong Dragon Power International Underwater Technology Consultant Service Limited | Private company limited by shares | Live |
| HONG KONG UNDERWATER TOURIST LIMITED | Private company limited by shares | Dissolved |
| Scuba Monster Underwater Photography Company Limited | Private company limited by shares | Live |
| Underwater Plus Production Limited | Private company limited by shares | Live |
| UNDERWATER EXPLORATION PRODUCTIONS LIMITED | Private company limited by shares | Dissolved |