| Inthemixuk Limited | Real estate | 2025 |
| Intrepid Growth Partners (UK) LLP | | 2025 |
| Intrepid Growth Partners Holdings (UK) Ltd | Financial services | 2025 |
| Ipseity Ltd | Education | 2024 |
| Isaac Auctioneers & Valuers Limited | Wholesale & retail | 2020 |
| Isabelle Darcy Ltd | Wholesale & retail | 2024 |
| Italian Ceramics Company Ltd | Wholesale & retail | 2022 |
| Itek I.T. Solutions Limited | Information & communication | 2008 |
| Ithaca Project Ltd | Information & communication | 2016 |
| Itrain IT Ltd | Information & communication | 2018 |
| ITS a RAP Limited | Information & communication | 2020 |
| Ivanhoe (Top House Rise Chingford) Limited | Households | 1962 |
| IVC Accounting Limited | Professional & scientific | 2019 |
| IVY Chimneys (Witham) Management Company Limited | Households | 2019 |
| Iwmcontracts Ltd | Energy | 2025 |
| J Bentley Limited | Construction | 2021 |
| J D Digital Sales Ltd | Wholesale & retail | 2024 |
| J D Rush Transport Ltd | Transport & logistics | 2026 |
| J Lovric Limited | Wholesale & retail | 2010 |
| J Mcwilliams & DAD Ltd | Construction | 2010 |
| J Meadows Limited | Transport & logistics | 2021 |
| J Morrison Ltd | Health & social care | 2022 |
| J Mullane Services Limited | Professional & scientific | 2019 |
| J P Kerr Ltd | Arts & recreation | 2012 |
| J.A & SON. Property Services Limited | Construction | 2025 |
| Jackson Electrics Ltd | Construction | 2010 |
| JAI & Sons Service Station Ltd | Wholesale & retail | 2018 |
| James Everett Photography Limited | Professional & scientific | 2010 |
| James Franklyn Developments Limited | Extraterritorial | 2023 |
| James Franklyn Holdings Limited | Extraterritorial | 2023 |
| James Mann Limited | Real estate | 1993 |
| Jamie Stevens Limited | Other services | 2010 |
| JAW Home Improvements Ltd | Construction | 2022 |
| Jawi Solutions Ltd | Professional & scientific | 2020 |
| JBA Developments Limited | Construction | 2008 |
| Jbliving Ltd | Construction | 2025 |
| JCG Engineering Ltd | Manufacturing | 2015 |
| JD Scaffolding (Essex) Ltd | Construction | 2026 |
| JDL Services & Management Limited | Water & waste | 2025 |
| JET WET Ltd | Administrative & support | 2025 |
| Jetstone Property Ltd | Construction | 2023 |
| JF Health and Medical Limited | Health & social care | 2023 |
| JHC Holdings Limited | Real estate | 2016 |
| Jimjams Spreads Ltd | Wholesale & retail | 2013 |
| JK Tech Productions Limited | Arts & recreation | 2017 |
| JKS Heating & Renewables Ltd | Construction | 2026 |
| JLA Facades Ltd | Construction | 2024 |
| JMC Mortgage Services Limited | Financial services | 2010 |
| JNE Electrical Ltd | Construction | 2023 |
| John Clark Services Limited | Construction | 2007 |
| John Green Physiotherapy Ltd | Health & social care | 2008 |
| John Lewin Consulting Ltd | Professional & scientific | 2023 |
| Jones Forestry and Timber Limited | Agriculture & fishing | 2024 |
| Jordan Capital Ltd | Education | 2021 |
| Joseph Dilworth Design Ltd. | Professional & scientific | 1999 |
| Joseph Fairs Limited | Wholesale & retail | 2010 |
| Joseph Matthew Property Consultancy Limited | Professional & scientific | 2023 |
| Josh LE Grove Entertainment Ltd | Arts & recreation | 2022 |
| Josie DOM Ltd | Administrative & support | 2015 |
| JPK Contractors Ltd | Construction | 2023 |
| JR Motor Engineers Limited | Wholesale & retail | 2012 |
| JR Security Systems Ltd | Administrative & support | 2022 |
| JS (Shaftesbury) Holdings Limited | Financial services | 2025 |
| JS Mid-Sussex Limited | Other services | 2019 |
| JSN Vintage Motor Car Engineering Limited | Professional & scientific | 2015 |
| JSP Floors Ltd | Construction | 2021 |
| JSS (Shaftesbury) Limited | Real estate | 2005 |
| JT Recycling Ltd | Wholesale & retail | 2025 |
| Jungle Adventure Limited | Arts & recreation | 2010 |
| Just Rims and Rubber Limited | Wholesale & retail | 2014 |
| Just Select Limited | Information & communication | 1999 |
| Just Wheel Repair Limited | Manufacturing | 2011 |
| JW Distillers Limited | Manufacturing | 2015 |
| JWG Group Essex Limited | Construction | 2015 |
| JWL Brickwork Limited | Construction | 2026 |
| JWP Automotive Ltd | Wholesale & retail | 2025 |
| K & a Estates Limited | Real estate | 2003 |
| K & R Projects Company Limited | Other services | 2002 |
| K & S Ceramic Tiling Limited | Construction | 2008 |
| K Anims Ltd | Transport & logistics | 2018 |
| K C Independent Respiratory Services Limited | Health & social care | 2015 |
| K D & Z Waller (Painters & Decorators) Limited | Construction | 2004 |
| K D Roofing Supplies & Services Ltd | Construction | 2021 |
| K J L Electrical Limited | Wholesale & retail | 2011 |
| K J Wallis Construction Limited | Construction | 2014 |
| K Swallow Limited | Information & communication | 2026 |
| K&J Housing Ltd | Real estate | 2026 |
| K.J. Wakeling Limited | Construction | 1998 |
| K33 Heating Ltd | Construction | 2024 |
| Kadmar Limited | Construction | 2017 |
| Kafften Concrete Repairs Limited | Construction | 2004 |
| Kafften Holdings Limited | Financial services | 2008 |
| Kafften Refurbishment Limited | Construction | 1998 |
| Kasfal Holdings Ltd | Wholesale & retail | 2016 |
| Kate Hurst Consulting Ltd | Health & social care | 2017 |
| Kaya EN Limited | Hospitality | 2026 |
| KBM Construction UK Limited | Administrative & support | 1999 |
| KCM Contracts Limited | Construction | 2016 |
| Keen Contractors Ltd | Construction | 2013 |
| Keith Martin & SON Limited | Transport & logistics | 2003 |