| Invoclick Ltd | Wholesale & retail | 2026 |
| Ioan Adrian Transport Ltd | Transport & logistics | 2014 |
| Ioan Natanael Samuel Ltd | Construction | 2025 |
| IOL Educational Trust | Education | 2001 |
| Ionut-Liviu Diaconu Ltd | Wholesale & retail | 2025 |
| IOT Property Ltd | Real estate | 2019 |
| IP Solutions Limited | Construction | 2022 |
| Ipproducts Limited | Information & communication | 2005 |
| IPS Apprenticeships Ltd | Extraterritorial | 2020 |
| IPS International Limited | Education | 1997 |
| Iquam Ltd | Health & social care | 2021 |
| IR Data Services Ltd | Information & communication | 2020 |
| Ircat Ltd | Construction | 2016 |
| IRH Mechanical Ltd | Construction | 2015 |
| Iris Technologies Ltd. | Wholesale & retail | 2014 |
| Isaac Newell Heritage Group CIC | Education | 2025 |
| Iscomi Group Limited | Wholesale & retail | 2012 |
| ISI Clean & Maintenance Ltd | Administrative & support | 2026 |
| Isite Civil Engineering Ltd | Construction | 2017 |
| Isite Solutions Ltd | Transport & logistics | 2017 |
| Island Park (Medway) Ltd | Real estate | 2020 |
| Islawyatt Services Limited | Health & social care | 2012 |
| ISM Air Conditioning Ltd | Construction | 2025 |
| ISO Duct Limited | Construction | 2015 |
| Isprom Limited | Health & social care | 2015 |
| ISS Electrical Ltd | Construction | 2023 |
| Issan Thai Ltd | Hospitality | 2019 |
| IT Clearance Ltd | Information & communication | 2025 |
| IT Clearance Solutions Ltd | Information & communication | 2018 |
| Itoo Electrical Ltd | Construction | 2013 |
| It’S Just an Estimate Ltd | Professional & scientific | 2025 |
| It’S Simply Furniture Ltd | Wholesale & retail | 2025 |
| IU Bars Ltd | Hospitality | 2025 |
| Ivanthorpe Limited | Real estate | 2006 |
| Ivory Hair Studio Ltd | Other services | 2017 |
| IVY Tree 2021 Limited | Wholesale & retail | 2021 |
| Ivyparty Ltd | Professional & scientific | 2023 |
| Iwade Developments Limited | Real estate | 1992 |
| IXS Digital Limited | Professional & scientific | 2025 |
| IYN Trans Ltd | Construction | 2025 |
| Izzie Estates Ltd | Real estate | 2024 |
| J & a Motors (Kent) Limited | Wholesale & retail | 2002 |
| J & K Properties (Kent) Ltd | Real estate | 2023 |
| J & MG Holdings Ltd | Real estate | 2016 |
| J & P Catt LLP | | 2020 |
| J & R Lifts Ltd | Construction | 2021 |
| J & T Construction (Southeast) Ltd | Administrative & support | 2013 |
| J and L Events UK Ltd | Other services | 2017 |
| J Bear Estates Ltd | Financial services | 2016 |
| J Cable Electrics Ltd | Construction | 2025 |
| J Clarkson Ltd | Construction | 2016 |
| J D Geering's Plumbing & Heating Limited | Construction | 1997 |
| J D Harper Construction Limited | Construction | 2024 |
| J D Harper Limited | Real estate | 2019 |
| J Day Collectibles Ltd | Wholesale & retail | 2023 |
| J F Construction Services (London) Limited | Construction | 2015 |
| J Fairbairn Building Service Ltd | Construction | 2025 |
| J G P Traffic Management Ltd | Public administration | 2026 |
| J J Smith Plumbing & Heating Limited | Construction | 2007 |
| J K Engineering Designs Limited | Professional & scientific | 2018 |
| J K Jointing (Services) Limited | Construction | 2010 |
| J K Podiatry Ltd | Health & social care | 2022 |
| J Lyne Property Solutions Ltd | Real estate | 2025 |
| J R C Plumbing Services Ltd | Construction | 2019 |
| J S B Haulage Limited | Other services | 2012 |
| J Sutton & Associates Ltd | Professional & scientific | 2021 |
| J&J Global Trading Ltd | Wholesale & retail | 2023 |
| J&J Healthcare Professionals Ltd | Administrative & support | 2022 |
| J&P Property Development Limited | Real estate | 2020 |
| J&Z Catering Limited | Hospitality | 2019 |
| J'S and G'S Properties Ltd | Wholesale & retail | 2025 |
| J-Mech Electrical Services Ltd | Construction | 2019 |
| J-Mech Plumbing and Heating Services Ltd | Construction | 2005 |
| J. Brown Interiors Ltd | Other services | 2013 |
| J.A Installations Ltd | Construction | 2025 |
| J.A.E Plumbing and Drainage Ltd | Construction | 2019 |
| J.B Construction (GB) Limited | Construction | 2003 |
| J.B. Properties (South East) Ltd | Real estate | 2012 |
| J.L. Wright Limited | Agriculture & fishing | 1950 |
| J.P Barker Holdings Ltd | Financial services | 2024 |
| J7 Electrical Services Ltd | Construction | 2022 |
| Jack Frost AC Limited | Construction | 2019 |
| Jack Loggin Lettings Limited | Real estate | 2012 |
| Jackhammer Clothing Ltd | Wholesale & retail | 2024 |
| Jacob Villas Limited | Households | 2004 |
| Jade Creative Solutions Ltd | Administrative & support | 2018 |
| Jade Emerson Ltd | Hospitality | 2025 |
| Jadenson Ltd | Information & communication | 2010 |
| Jael Property Solutions Ltd | Real estate | 2025 |
| JAG Transport Limited | Transport & logistics | 2003 |
| Jaggers of Rochester Limited | Manufacturing | 2024 |
| Jagz Sandhu Ltd | Administrative & support | 2023 |
| JAH Heating Services Limited | Construction | 2019 |
| Jaiyeolateju Ltd | Public administration | 2020 |
| James Archer Limited | Professional & scientific | 2017 |
| James Clarke Engineering Limited | Professional & scientific | 2017 |
| James Frost Transport Services Ltd | Transport & logistics | 2014 |
| James Taplin Music Ltd. | Education | 2023 |
| Jameszoe Family Partnership LLP | | 2021 |
| Jamie B J Limited | Construction | 2015 |