| IL Vino (Shahaj) Limited | Hospitality | 2013 |
| Imber House Management Company Limited | Households | 2003 |
| Immaculate Confections Limited | Manufacturing | 2019 |
| Imperial M Contractors Ltd | Construction | 2020 |
| IMR Education Ltd | Other services | 2014 |
| IN2UIT Limited | Arts & recreation | 2017 |
| Incir Limited | Hospitality | 2023 |
| Indemandify Ltd | Wholesale & retail | 2022 |
| Infantino Consultants Limited | Professional & scientific | 2026 |
| Infantino Investments Limited | Real estate | 2011 |
| Infralay UK Limited | Other services | 2025 |
| Inglewhite Meadow Residents Management Company Limited | Households | 2021 |
| Ingrao-Mclarty Holdings Limited | Real estate | 2022 |
| Ingress Park Greenhithe (DWH) Management Company Ltd | Households | 2004 |
| Inholm Residents Management Company Limited | Households | 2021 |
| Injection Moulding Services Ltd | Manufacturing | 2024 |
| Injna Ltd | Health & social care | 2012 |
| Inkidz Ltd | Wholesale & retail | 2025 |
| Inline-Support Ltd | Information & communication | 2023 |
| Innovation MEP Limited | Construction | 2019 |
| Insignia Investments Limited | Professional & scientific | 2007 |
| Insignia Residential Management Limited | Households | 2020 |
| Inspiring Insights (UK) Ltd | Professional & scientific | 2022 |
| Inspiring Insights Ltd | Professional & scientific | 2014 |
| Instock Hardware Limited | Administrative & support | 1999 |
| Intelligent Fones Ltd | Information & communication | 2018 |
| Intellyts Limited | Information & communication | 2024 |
| Inter-Nuncio Limited | Transport & logistics | 2020 |
| Interm IT (UK) Limited | Information & communication | 2014 |
| International PR Limited | Extraterritorial | 2005 |
| Internet Names 2007 Ltd | Administrative & support | 2007 |
| Interstellar Projects Limited | Professional & scientific | 2023 |
| Invader Films Limited | Information & communication | 2025 |
| Invicta Ventures Limited | Real estate | 2022 |
| Invicter Property Limited | Administrative & support | 2016 |
| Inyapants Ltd | Hospitality | 2026 |
| Ioan Grigor Ltd | Construction | 2012 |
| Ipser Limited | Extraterritorial | 2003 |
| Iron Wolf Systems Ltd | Construction | 2023 |
| Ironworks (Leeds) Management Company Limited | Real estate | 2022 |
| Irwell Riverside Management Company Limited | Households | 2017 |
| Isabella Place Two (Chafford Hundred) Management Company Limited | Households | 2003 |
| Isaiah Pierre Ltd | Wholesale & retail | 2023 |
| Isis Maintenance Limited | Construction | 2007 |
| Isis Restoration Limited | Construction | 1998 |
| IT Global Services Limited | Manufacturing | 2010 |
| Italia Holdings Ltd | Hospitality | 2016 |
| Iterum AI Ltd | Information & communication | 2023 |
| IVY Farm (Royston) Management Company Limited | Households | 2014 |
| IVY Online Ltd | Wholesale & retail | 2025 |
| J & J Installations Ltd | Professional & scientific | 2015 |
| J & L Scaffolding Services Ltd | Construction | 2017 |
| J Burke Consultancy Limited | Professional & scientific | 2018 |
| J H Barker and Sons Limited | Agriculture & fishing | 2017 |
| J Lythall Ltd | Health & social care | 2026 |
| J Mallett Consultancy Ltd | Information & communication | 2026 |
| J Mean Building Services Limited | Construction | 2014 |
| J Tyler & Sons Ltd | Construction | 2019 |
| J W Munroe Groundworks Limited | Extraterritorial | 2004 |
| J W Wheatley Ltd | Information & communication | 2017 |
| Jack Louis Hair Styling Ltd | Other services | 2020 |
| Jackdaw TV Ltd | Information & communication | 2014 |
| Jackie Pearson Financial Services Ltd | Financial services | 2026 |
| Jackson's Place (Kerridge) Residents Association Limited | Households | 2001 |
| Jacqueline Gbenoba Limited | Health & social care | 2019 |
| Jade Hair Limited | Other services | 2017 |
| Jade Signs (UK) Limited | Manufacturing | 2005 |
| Jago J Electrical Limited | Construction | 2014 |
| Jaguar Pest Control Limited | Administrative & support | 2013 |
| Jalisha Properties Limited | Real estate | 2023 |
| James Enterprise Limited | Wholesale & retail | 2025 |
| James Holmes Court (Management) Limited | Households | 1986 |
| James Linde Limited | Wholesale & retail | 1957 |
| Jammed Investments Ltd | Real estate | 2014 |
| Jarek Access Services Ltd | Construction | 2024 |
| Jayelander Ltd | Real estate | 2025 |
| Jazz Residents Management Company Limited | Households | 2004 |
| JB Commercial Repair Ltd | Wholesale & retail | 2016 |
| Jbdl Holdings Limited | Financial services | 2026 |
| JBF Haulage Ltd | Transport & logistics | 2019 |
| JBF Parking Services Ltd | Transport & logistics | 2023 |
| JBF Storage & Distribution Ltd | Transport & logistics | 2026 |
| Jbos Holdings Limited | Administrative & support | 2007 |
| JBS Legacy Ltd | Real estate | 2025 |
| JC Flooring (Contracts) Ltd | Wholesale & retail | 2013 |
| Jcea Property Ltd | Real estate | 2024 |
| JD Transfers Ltd | Transport & logistics | 2023 |
| JDM Financials Ltd | Financial services | 2022 |
| JDS Tax Services Ltd | Professional & scientific | 2024 |
| JEC Property Investments Ltd | Real estate | 2018 |
| Jelliss & Co. Limited | Information & communication | 2005 |
| Jenner Court Freehold Limited | Households | 2013 |
| Jennings Property Holdings Limited | Real estate | 2016 |
| Jerry Greig Ltd | Professional & scientific | 2016 |
| Jetsie Limited | Transport & logistics | 1978 |
| JF Autos Herts Ltd | Wholesale & retail | 2025 |
| JG Floors Limited | Construction | 2019 |
| JG Tiling Ltd | Construction | 2023 |
| JGO Accounting and Technology Services Ltd | Information & communication | 2016 |
| Jireh Caring Company Limited | Health & social care | 2023 |