| IL Mattone Limited | Real estate | 2025 |
| Ilusiv Shades Limited | Wholesale & retail | 2024 |
| IMC Locums Limited | Information & communication | 2016 |
| Impacte Limited | Information & communication | 2019 |
| Imre Jambor Autos Ltd | Wholesale & retail | 2015 |
| IN2 Plastics Limited | Manufacturing | 2004 |
| Infinite Mobile Homes Limited | Real estate | 2021 |
| Ingrid Weel Media Ltd | Information & communication | 2013 |
| Inherited Disorders of Connective Tissue Limited | Professional & scientific | 2020 |
| Initio Design Limited | Manufacturing | 2014 |
| Innervate Career Services Limited | Education | 2012 |
| Innosource Cars Ltd | Wholesale & retail | 2023 |
| Insolvency Solutions Limited | Professional & scientific | 2017 |
| Intellectual Pixels Limited | Administrative & support | 2019 |
| Inter Primos Ltd | Construction | 2019 |
| Interco Management Ltd | Administrative & support | 2008 |
| International Agri Investments Ltd | Professional & scientific | 2025 |
| International Waterski & Wakeboard Federation Limited | Arts & recreation | 2003 |
| Inva & Co Limited | Hospitality | 2026 |
| Invesco Properties Ltd | Real estate | 2015 |
| Investec Property Group Ltd | Construction | 2025 |
| Iorana Cruises Ltd | Transport & logistics | 2023 |
| Ioresource (UK) Limited | Wholesale & retail | 2017 |
| Island Boats Ltd | Wholesale & retail | 1991 |
| Itask Limited | Information & communication | 2018 |
| Itheil Limited | Information & communication | 2015 |
| Itia Transport Ltd | Transport & logistics | 2026 |
| Ivory Property Management Ltd | Real estate | 2022 |
| IVP Health Ltd | Health & social care | 2023 |
| J Batey Ltd | Arts & recreation | 2018 |
| J Business Network Global Ltd | Other services | 2016 |
| J C Facilities Limited | Manufacturing | 2013 |
| J R Aviation Services Limited | Manufacturing | 2025 |
| J W Adams and Sons Limited | Construction | 2004 |
| J White Commercials Ltd | Wholesale & retail | 2019 |
| J. Mackenzie Carpentry & Joinery Ltd | Construction | 2016 |
| J.A.C.K. Educational Consultancy Limited | Professional & scientific | 2023 |
| J.Patrick Consulting Limited | Professional & scientific | 2025 |
| J.Perry Consultancy Ltd | Health & social care | 2026 |
| Jagatwani London Limited | Information & communication | 2025 |
| Jake Kensley Ltd | Information & communication | 2025 |
| JAM IT Services Ltd | Information & communication | 2023 |
| James Ramsey Limited | Real estate | 2006 |
| Jangos Food Ltd | Wholesale & retail | 2025 |
| Jarvis Innovation Limited | Professional & scientific | 2025 |
| JAS Management Consultancy Limited | Professional & scientific | 2018 |
| JB Construction Mouldings Ltd | Manufacturing | 2022 |
| JBB Global Ltd | Other services | 2015 |
| JCD Aviation Consulting Limited | Professional & scientific | 2023 |
| Jemna Limited | Information & communication | 2019 |
| Jewel Electrical Services Limited | Construction | 2010 |
| Jewel Facilities Management Ltd | Real estate | 2017 |
| Jfpib Limited | Financial services | 2022 |
| JFR Training Limited | Administrative & support | 1989 |
| JG Ingle's Service Ltd | Construction | 2024 |
| JH Plumbing Limited | Construction | 2025 |
| Jinyue Education and Tourism Ltd | Administrative & support | 2024 |
| JJA Ashill Limited | Professional & scientific | 2017 |
| JK Consulting Services Limited | Professional & scientific | 2026 |
| JNK Rail Ltd | Construction | 2015 |
| Jobland Limited | Information & communication | 2024 |
| JOE Regent Limited | Hospitality | 2026 |
| Joeysummer Ltd | Construction | 2021 |
| Johnson & Jones Limited | Real estate | 2005 |
| Johnson Downes Consulting Limited | Professional & scientific | 2011 |
| Jolly UP Ltd | Health & social care | 2024 |
| Jonathan Clarke Ltd | Wholesale & retail | 2018 |
| Jones Tree Specialists Ltd | Agriculture & fishing | 2024 |
| JP Liberty Limited | Health & social care | 2024 |
| JPA Carpentry Ltd | Manufacturing | 2022 |
| JPC Waste Management Services Ltd | Water & waste | 2021 |
| JRM Engineering Limited | Professional & scientific | 2019 |
| JSC Construction Ltd | Construction | 2026 |
| Jsight Ltd | Health & social care | 2024 |
| Julesinc Limited | Information & communication | 2023 |
| June Whittle Ltd | Professional & scientific | 2010 |
| JVI Trees Ltd | Administrative & support | 2025 |
| JVN Consulting Limited | Manufacturing | 2017 |
| K Electrical Solutions Limited | Construction | 2018 |
| K P D Hussey Mobile Welding Limited | Construction | 2015 |
| K Property Solutions Limited | Real estate | 2023 |
| K-Squared Productions | Arts & recreation | 2019 |
| K9 Oral Care Ltd | Other services | 2014 |
| Kadick Limited | Real estate | 2022 |
| Kaida Marketing Services Ltd | Professional & scientific | 2025 |
| Kairos Athena Limited | Professional & scientific | 2026 |
| Karl Farrant Marine Limited | Other services | 2009 |
| Karmaday Consulting Ltd | Professional & scientific | 2024 |
| Kates Chocolates Food Ltd | Manufacturing | 2017 |
| Katriina North Ltd | Wholesale & retail | 2021 |
| Kautt & BUX (Logistics) Ltd | Transport & logistics | 2016 |
| Kaybros Limited | Hospitality | 1996 |
| KBH Roofing Limited | Construction | 2026 |
| Kbys Autos Limited | Wholesale & retail | 2018 |
| Keane Developments (London) Limited | Construction | 2026 |
| Keep Fire Solutions UK Ltd | Construction | 2026 |
| Kendrix Build Group Ltd | Professional & scientific | 2024 |
| Kenton Consulting Limited | Professional & scientific | 2022 |
| Kesterport Limited | Wholesale & retail | 1977 |
| Key Stays Living Ltd | Administrative & support | 2026 |