| Isaac Innovative Hair Ltd | Other services | 2023 |
| Isaac Training Academy Ltd | Other services | 2025 |
| IT Changes Limited | Information & communication | 2012 |
| IT247 Solutions Ltd | Information & communication | 2020 |
| Itas Evolve Ltd | Extraterritorial | 2013 |
| Itas Properties Limited | Real estate | 2023 |
| Itech MK Ltd | Administrative & support | 2017 |
| ITG Management Services Limited | Professional & scientific | 2012 |
| Itnoa Eco Ltd | Construction | 2023 |
| Itnoa Fuel Station Ltd | Wholesale & retail | 2026 |
| Itnoa Fuelling Group Ltd | Wholesale & retail | 2026 |
| Itnoa Properties Ltd | Real estate | 2024 |
| Izzy Europe Ltd | Wholesale & retail | 2024 |
| J Henry Assessments Ltd | Professional & scientific | 2023 |
| J J H Construction Limited | Construction | 2005 |
| J M C Agencies Ltd | Wholesale & retail | 2013 |
| J R Training Services Ltd | Administrative & support | 2006 |
| J W Cook & SON LP | | 2011 |
| J&H Consultancy Limited | Administrative & support | 2019 |
| J&L Custom Coachbuilders Ltd | Manufacturing | 2026 |
| J.C Nails Ltd | Other services | 2025 |
| J.M. Farms Limited | Real estate | 1976 |
| J.P.King Electrical Ltd | Construction | 2012 |
| JA Mortgage and Protection Ltd | Administrative & support | 2025 |
| Jaan Associates Limited | Extraterritorial | 2014 |
| Jack Francis Design Ltd | Professional & scientific | 2022 |
| Jacmon Limited | Information & communication | 2025 |
| Jacob Brothers Ltd | Wholesale & retail | 2024 |
| JAF Property Management Limited | Real estate | 2014 |
| James Eltherington Design Limited | Information & communication | 2009 |
| James Maciver Costumes Limited | Administrative & support | 2015 |
| Jaydprop Estate Limited | Real estate | 2019 |
| JBS FLT Ltd | Education | 2023 |
| JCR Holdco Limited | Financial services | 2024 |
| JDL IT Consultancy Limited | Information & communication | 2021 |
| JEB Consultancy Ltd | Professional & scientific | 2025 |
| Jecd Limited | Other services | 2019 |
| Jericho Global Network Ltd | Other services | 2017 |
| Jerk N RUM Ltd | Hospitality | 2020 |
| Jessica Cunniffe Ltd | Professional & scientific | 2023 |
| JH Darts Ltd | Arts & recreation | 2026 |
| JH General Services Limited | Construction | 2016 |
| JJ Build NR1 Ltd | Construction | 2023 |
| JJM Consulting & Environmental Services Ltd | Agriculture & fishing | 2022 |
| JJM Properties Holdings Limited | Real estate | 2025 |
| Jkae Property Ltd | Real estate | 2022 |
| JKT Care Services Ltd | Health & social care | 2024 |
| JLD Medical Ltd | Health & social care | 2019 |
| JML Digital Limited | Administrative & support | 2021 |
| JMS Realestate Private Ltd | Real estate | 2023 |
| John Elia Limited | Wholesale & retail | 2018 |
| Johnstons (SR CH) Limited | Health & social care | 2003 |
| Jojo Hair Lounge Ltd | Other services | 2023 |
| Jorelle Limited | Professional & scientific | 2025 |
| Joyelle Properties UK Ltd | Real estate | 2022 |
| Joyfes Healthcare Services Ltd | Health & social care | 2014 |
| JPL Roofing Ltd | Construction | 2026 |
| JRP Automotive Limited | Wholesale & retail | 2016 |
| JSJ Assets Ltd | Construction | 2013 |
| JSL Roofing Ltd | Construction | 2017 |
| JST Haulage Limited | Transport & logistics | 2017 |
| Juleson Moore Limited | Construction | 2016 |
| Juniper Hill Silver Limited | Wholesale & retail | 2023 |
| Just Global Investments Ltd | Financial services | 2012 |
| Just Incredible Cleaning Limited | Administrative & support | 2020 |
| Just Mots (Newport Pagnell) Ltd | Wholesale & retail | 2025 |
| Just Sign Here Ltd | Professional & scientific | 2009 |
| Justice GAS Services Ltd | Construction | 2021 |
| Justice Medica Ltd | Health & social care | 2024 |
| K J Hill Limited | Construction | 2002 |
| K Marsh Consulting Limited | Professional & scientific | 2014 |
| K Sport & Injury Rehabilitation Ltd | Other services | 2023 |
| K-Five Investment Properties Limited | Real estate | 2021 |
| K-Five Group Limited | Extraterritorial | 2018 |
| K.P.E Event Technical Services Limited | Information & communication | 2015 |
| K8 Transitions Ltd | Professional & scientific | 2018 |
| Kaizendo Services Limited | Information & communication | 2026 |
| Kamilia Limited | Hospitality | 2022 |
| Karmall Properties Limited | Households | 2023 |
| Karnik Holdings Limited | Financial services | 2019 |
| Kasango Limited | Transport & logistics | 2022 |
| Katy Lewis Limited | Professional & scientific | 2015 |
| Kcpb Holdings Ltd | Financial services | 2026 |
| Keanu Logistics Ltd | Transport & logistics | 2024 |
| Keegan Planning Ltd | Professional & scientific | 2025 |
| Kemadi Holdings Limited | Financial services | 2025 |
| Kemadi Homes Limited | Real estate | 2020 |
| Kemadi Lettings Limited | Real estate | 2026 |
| KEN Sutton & Associates Limited | Professional & scientific | 2017 |
| Kentmere Group Limited | Financial services | 2024 |
| Kessiful Delivery Service Ltd | Transport & logistics | 2019 |
| Kestrel Heathrow Ltd | Real estate | 2019 |
| Kevin SJ Cross Ltd | Construction | 2016 |
| Kevin Todd Architectural Ltd | Professional & scientific | 2023 |
| Key Library Ltd | Wholesale & retail | 2023 |
| Key Serv Ltd | Wholesale & retail | 2024 |
| Kikoshop Ltd | Wholesale & retail | 2026 |
| Kilning ME Softly Ltd | Wholesale & retail | 2024 |
| Kimchidragon Limited | Wholesale & retail | 2024 |
| Kings Road Fashions Limited | Wholesale & retail | 2006 |