| Invita Maintenance Ltd | Construction | 2023 |
| IP Aviation Ltd | Professional & scientific | 2010 |
| IP TEC Limited | Administrative & support | 2011 |
| IP Tech Limited | Professional & scientific | 2021 |
| Ipswich Student Rentals Ltd | Real estate | 2020 |
| IRB Consultancy Limited | Administrative & support | 2010 |
| Israel Limited | Extraterritorial | 2009 |
| Ithrive Initiative C.I.C. | Education | 2024 |
| Iwantmysay Ltd | Information & communication | 2014 |
| J & F Building Services Limited | Construction | 2018 |
| J Mall Limited | Wholesale & retail | 2015 |
| J'N'M Lettings Ltd | Real estate | 2026 |
| J.E.P. Management Consultants Limited | Real estate | 1992 |
| J.Matthews Ltd | Transport & logistics | 2024 |
| J.P.S Security Ltd | Administrative & support | 2018 |
| Jacobs Paint Limited | Manufacturing | 2025 |
| Jaggar Accountants Ltd | Professional & scientific | 2020 |
| Jahn(Maskiner),Limited | Manufacturing | 1929 |
| JAM Childcare Solutions Limited | Health & social care | 2016 |
| JAM Creations Ltd | Professional & scientific | 2012 |
| James Calver Limited | Construction | 2007 |
| James Tristan Investments Ltd | Financial services | 2013 |
| Javiation Limited | Transport & logistics | 1996 |
| Jayessex Limited | Agriculture & fishing | 2012 |
| JB Chinese Limited | Hospitality | 2026 |
| JB Studio LDN Limited | Information & communication | 2023 |
| JBC ZQH Chinese Ltd | Hospitality | 2022 |
| JBM Fabrications Ltd | Manufacturing | 2024 |
| JBR Animation Limited | Information & communication | 2020 |
| JC Technology Consulting Ltd | Information & communication | 2022 |
| Jclm Maintenance Ltd | Construction | 2025 |
| JD Aero Interiors Ltd | Other services | 2025 |
| JD Construction & Consultancy Ltd | Construction | 2025 |
| JDF Mechanical Services Ltd | Wholesale & retail | 2025 |
| JDM Electrical Solutions Ltd | Construction | 2026 |
| Jennybirdi Consulting Limited | Professional & scientific | 2024 |
| Jeorj Assets Limited | Construction | 2026 |
| Jessica Holdings Limited | Financial services | 2019 |
| Jevyco Ltd | Real estate | 2025 |
| JF Weddings Ltd | Wholesale & retail | 2015 |
| JFL Services (Essex) Ltd | Other services | 2026 |
| JG Cars and Vans Ltd | Wholesale & retail | 2023 |
| Jivey Audio Group Ltd | Information & communication | 2022 |
| Jjcs Limited | Education | 2013 |
| Jklass Cakery Limited | Manufacturing | 2018 |
| JLS Nominees Ltd | Extraterritorial | 2020 |
| JLT Property Development Ltd | Households | 2026 |
| JMB Services (Essex) Limited | Transport & logistics | 2025 |
| JMC Accountants Limited | Professional & scientific | 2009 |
| JOE the Lock Ltd | Wholesale & retail | 2023 |
| John M. Mcnamara Limited | Professional & scientific | 2002 |
| Jolly Butchers (Stoke Newington) Limited | Hospitality | 2010 |
| Jonathan Desousa Properties Ltd | Real estate | 2024 |
| Jonesandroamco Ltd | Wholesale & retail | 2025 |
| Joosy Ltd | Wholesale & retail | 2026 |
| Joseph Barnes Wines Limited | Wholesale & retail | 2000 |
| Jp's Wild Honey Ltd | Hospitality | 2020 |
| Jperks Limited | Professional & scientific | 2025 |
| JPL Servicing Ltd | Wholesale & retail | 2014 |
| JPO Property Ltd | Real estate | 2025 |
| JR Astro Craft Ltd | Wholesale & retail | 2026 |
| Jrte Investments Limited | Real estate | 2021 |
| JS CAD Design Ltd | Professional & scientific | 2021 |
| JS Land & Property Ltd | Financial services | 2023 |
| JSS (Chelmsford) Ltd | Real estate | 2017 |
| JT Elite Car Care Ltd | Administrative & support | 2026 |
| JTL Van Lock Installers Ltd | Other services | 2023 |
| Judestar Properties Ltd | Real estate | 2024 |
| Julian Little Communications Ltd | Professional & scientific | 2020 |
| JUMPSTART24 Ltd | Wholesale & retail | 2024 |
| Just Another Salon & Training Ltd | Other services | 2025 |
| Just Free From Foods Ltd | Administrative & support | 2018 |
| JVP Leisure Limited | Arts & recreation | 2011 |
| JY Damproofing Limited | Construction | 2026 |
| K & a Contract Services Limited | Wholesale & retail | 2017 |
| K & a Flooring Limited | Wholesale & retail | 2016 |
| K & W Exports Ltd | Wholesale & retail | 2017 |
| K and R Executive Ltd | Financial services | 2006 |
| K H Dunmow Management Ltd | Households | 2018 |
| K S J Estates Ltd | Real estate | 2021 |
| K Sykes Electrical Services Limited | Other services | 1993 |
| K.C. Investments Limited | Financial services | 1998 |
| Kabrams Consulting Limited | Professional & scientific | 2017 |
| Kahlua Limited | Professional & scientific | 2010 |
| Karma Air Ltd | Transport & logistics | 2022 |
| Kasparian Ltd | Real estate | 2025 |
| KAT Clay Studio Ltd | Arts & recreation | 2022 |
| Katherine Alice Limited | Other services | 2017 |
| Kave Aesthetics Ltd | Other services | 2026 |
| Kawecki Ltd | Other services | 2014 |
| Kdubyall Limited | Construction | 2018 |
| Keithya Limited | Financial services | 2022 |
| Keld Trading Limited | Financial services | 2017 |
| Kelvedon & District Angling Association Ltd | Arts & recreation | 2026 |
| Kempson White Limited | Wholesale & retail | 2017 |
| Kerb Appeal Wheel Refurbishment Limited | Administrative & support | 2022 |
| Keystone Technology Limited | Construction | 2001 |
| Kidzfair CIC | Administrative & support | 2024 |
| Killala Films Limited | Arts & recreation | 2014 |
| Kilnfield Barns Management Company Limited | Households | 2023 |