| Junior Transport Limited | Transport & logistics | 2025 |
| Juniper Property Ltd | Real estate | 2019 |
| Junkaway Southampton Limited | Water & waste | 2025 |
| Junnk Limited | Arts & recreation | 2013 |
| Jupiter Bay Limited | Professional & scientific | 2018 |
| Jupiter Properties Limited | Construction | 1994 |
| JURA42 Technology Ltd | Administrative & support | 2025 |
| Jure Ltd | Professional & scientific | 2015 |
| Jurez Consulting Limited | Professional & scientific | 2006 |
| Jurnol Limited | Information & communication | 2026 |
| Just Account IT Limited | Professional & scientific | 2025 |
| Just Accounting Media Limited | Administrative & support | 2003 |
| Just ADD Zest Limited | Professional & scientific | 2006 |
| Just Balls Sporting Limited | Wholesale & retail | 2018 |
| Just BE Maritime Ltd | Professional & scientific | 2021 |
| Just Brand Group Limited | Financial services | 2020 |
| Just FIX and Go Ltd | Wholesale & retail | 2024 |
| Just Floor Care Ltd | Administrative & support | 2025 |
| Just Gardens (Sussex) Limited | Administrative & support | 2010 |
| Just Hoting Limited | Manufacturing | 2024 |
| Just Like YOU Limited | Health & social care | 2022 |
| Just Mortgaging Limited | Financial services | 2026 |
| Just Natural Ltd | Extraterritorial | 2021 |
| Just Park Southampton Limited | Hospitality | 2025 |
| Just Right Home Care Ltd | Health & social care | 2020 |
| Just Right Resources Ltd | Administrative & support | 2024 |
| Just Skin Aesthetic Clinic Ltd | Other services | 2022 |
| Just the Property Ltd | Real estate | 2024 |
| Just Think Roofing Ltd | Construction | 2024 |
| Just Trades Group Ltd | Information & communication | 2026 |
| Just-Raf Ltd | Transport & logistics | 2025 |
| Justcroft International Limited | Information & communication | 1988 |
| Justice for Hair Ltd | Other services | 2014 |
| Justin Day Services Limited | Manufacturing | 2012 |
| Justin Elliott QS Services Limited | Professional & scientific | 2018 |
| Justinian Park Management Company Limited | Households | 1977 |
| Justletgo Ltd | Other services | 2014 |
| Justmike Limited | Transport & logistics | 2022 |
| Justyn Grant Ltd | Financial services | 2012 |
| JV Digital Ventures Ltd | Wholesale & retail | 2026 |
| JV Info Limited | Professional & scientific | 2025 |
| JV Rail Solutions Ltd | Construction | 2015 |
| JV Water Solutions Ltd | Construction | 2025 |
| JVF CT RAD Ltd | Health & social care | 2021 |
| JVR Electrical & Building Services Ltd | Construction | 2019 |
| JW Builders & DAD Ltd | Construction | 2020 |
| JW Clinical Endoscopist Ltd | Health & social care | 2022 |
| JW Composites Limited | Professional & scientific | 2016 |
| JW HR Solutions Ltd | Administrative & support | 2018 |
| JW Operational Solutions Ltd | Professional & scientific | 2017 |
| JWB01 Ltd | Other services | 2022 |
| JWH Building Contractors Ltd | Construction | 2021 |
| Jwin Limited | Administrative & support | 2026 |
| JWM Asset Management Ltd | Professional & scientific | 2016 |
| Jwtm Limited | Construction | 2023 |
| Jwtw Properties Ltd | Transport & logistics | 2021 |
| JX Construction Limited | Construction | 2018 |
| JY China Garden Limited | Hospitality | 2022 |
| JZ Oval Limited | Real estate | 2024 |
| K & D Beare Roofing Limited | Construction | 2017 |
| K & F Consult Limited | Professional & scientific | 2021 |
| K & J Contracts Limited | Construction | 2006 |
| K & J Sparkle Cleaning Solutions Ltd | Administrative & support | 2025 |
| K & L Support Services Limited | Administrative & support | 2013 |
| K & N Finishers Southern Limited | Manufacturing | 2002 |
| K & N Properties & Developments Ltd | Real estate | 2015 |
| K & S TRADING1 Limited | Hospitality | 2017 |
| K a Bevis Barbier Limited | Administrative & support | 2026 |
| K Ajel Ltd | Health & social care | 2015 |
| K AM Global Concepts Ltd | Health & social care | 2022 |
| K and D Driver Hire Ltd | Transport & logistics | 2018 |
| K and T Properties Limited | Real estate | 2015 |
| K Barber Consulting Ltd | Construction | 2014 |
| K Base Media Ltd | Information & communication | 2018 |
| K C Records Ltd | Information & communication | 2022 |
| K C T Electrics Limited | Construction | 1997 |
| K Dragon Ltd | Hospitality | 2024 |
| K Dragon Records Limited | Information & communication | 2021 |
| K Griffiths BRR Ltd | Real estate | 2023 |
| K Griffiths HMO Ltd | Real estate | 2023 |
| K L J Consulting Limited | Administrative & support | 2022 |
| K Lucas Cafe Limited | Hospitality | 2018 |
| K M B Solutions Limited | Professional & scientific | 1998 |
| K M H GAS Limited | Construction | 2010 |
| K N K Properties (Soton) Ltd | Real estate | 2022 |
| K R Fifteen Media Ltd | Information & communication | 2020 |
| K R P Express Transport Ltd | Transport & logistics | 2005 |
| K R Tree Care Limited | Administrative & support | 2021 |
| K S Mechanical Hampshire Limited | Construction | 2001 |
| K S T Holdings Limited | Financial services | 2018 |
| K Sidhu Construction Limited | Construction | 2021 |
| K T S Property Investments Limited | Real estate | 2001 |
| K Y Tong & Co Ltd | Professional & scientific | 1996 |
| K&A Barber Shop Limited | Other services | 2025 |
| K&G Equity Partners Ltd | Financial services | 2025 |
| K&G Haywood Ltd | Hospitality | 2017 |
| K&G Metalcraft Ltd | Manufacturing | 2013 |
| K&K Momo Ventures Ltd | Hospitality | 2025 |
| K&N Estate Holdings Limited | Real estate | 2025 |
| K&N Projects Ltd | Real estate | 2018 |