| IMG Capital Ltd | Real estate | 2024 |
| Impact Diagnostics Limited | Health & social care | 2009 |
| IN and OUT Inventories (UK) Ltd | Construction | 2011 |
| Inbam Ltd | Health & social care | 2020 |
| Incrementum Business Development Ltd | Administrative & support | 2023 |
| Independence & Wellbeing Project CIC | Health & social care | 2026 |
| Independent Professional Staffing Ltd | Administrative & support | 2024 |
| India Waudby Ltd | Health & social care | 2023 |
| Indian Barry Ltd | Hospitality | 2026 |
| Indian High Street Ltd | Hospitality | 2025 |
| Indian Kitchen 2025 Ltd | Hospitality | 2025 |
| Infinity Franchise Ltd | Professional & scientific | 2025 |
| Infinity Hair Loss Clinic Ltd | Other services | 2020 |
| Inspired Learners Ltd | Education | 2016 |
| Inspired Learners School Ltd | Education | 2023 |
| Install Construction Ltd | Construction | 2025 |
| Install Fabrications Ltd | Manufacturing | 2019 |
| Install Integrated Skips Limited | Water & waste | 2016 |
| Install Waste Management Ltd | Water & waste | 2016 |
| Integrated Graphics Limited | Manufacturing | 1991 |
| Intelligent Project Design Services Ltd | Professional & scientific | 2015 |
| Interbulk Limited | Transport & logistics | 2000 |
| Interstar Building & Utilities Limited | Construction | 2026 |
| Into-It Accounting Limited | Professional & scientific | 2017 |
| Inupon Limited | Arts & recreation | 2020 |
| Invent Software Limited | Information & communication | 2003 |
| Ioan Investment Limited | Financial services | 2020 |
| Ionut&Darius&Luca Ltd | Construction | 2026 |
| Ipdc Services Ltd | Construction | 2017 |
| IRB Controls Limited | Professional & scientific | 2022 |
| Irene's Supper Bar Limited | Hospitality | 2001 |
| ISA Solutions Ltd | Information & communication | 2023 |
| ISK Tech Limited | Information & communication | 2024 |
| Island Scaffolding Services Limited | Construction | 2019 |
| Island SUP Ltd | Wholesale & retail | 2019 |
| Island Upcycling Ltd | Manufacturing | 2024 |
| Islander Shipping Limited | Transport & logistics | 2021 |
| ISO GUY Ltd | Professional & scientific | 2013 |
| Istyle Vale of Glamorgan Ltd | Wholesale & retail | 2022 |
| IT Data Support Ltd | Manufacturing | 2016 |
| IT Takes 7 Seconds Limited | Professional & scientific | 2006 |
| It's Snow Joke Ltd | Manufacturing | 2018 |
| It-Helpdesk.Com Limited | Information & communication | 2008 |
| Ivor Street Stores Ltd | Wholesale & retail | 2024 |
| J & K Windows 2021 Limited | Manufacturing | 2021 |
| J Donne Landscaping and Building Services Limited | Construction | 2017 |
| J Frankel Ltd | Health & social care | 2019 |
| J Giddings Plumbing and Heating Limited | Construction | 2026 |
| J J & F Limited | Real estate | 2001 |
| J Marks Logistics Ltd | Transport & logistics | 2018 |
| J R Heating Services Ltd | Construction | 2017 |
| J S Bowsher Limited | Construction | 1988 |
| J.O.W Solutions Ltd | Construction | 2024 |
| Jacky Knowles Consultancy Ltd | Professional & scientific | 2014 |
| Jacquie’S Fruit & Vegetables Ltd | Wholesale & retail | 2022 |
| Jadd Group Ltd | Construction | 2025 |
| JAG Hire and Sales Ltd | Administrative & support | 2024 |
| James Creegan Limited | Professional & scientific | 2018 |
| James Garnett Business Change Analysis Limited | Administrative & support | 2014 |
| James GS Electrical Limited | Construction | 2024 |
| Jarlie Investments Limited | Real estate | 2020 |
| Jarlie Properties Limited | Real estate | 2021 |
| Jarrod`S Specialist Carpentry Limited | Construction | 2009 |
| Jason Thomas Carpentry Services Ltd | Construction | 2013 |
| Jathem Medical Solutions Limited | Health & social care | 2022 |
| JAY the DON Barbers Ltd | Other services | 2020 |
| Jaya Enterprises Ltd | Administrative & support | 2024 |
| JBD Equestrian Limited | Agriculture & fishing | 2025 |
| Jbrprime Ltd | Other services | 2025 |
| JD Auto Services (SW) Ltd | Wholesale & retail | 2026 |
| JD Training Limited | Professional & scientific | 2012 |
| Jd-Fire & Safety Limited | Public administration | 2024 |
| JDC11 Ltd | Hospitality | 2024 |
| JDR Logistics Limited | Transport & logistics | 2023 |
| JE King & SON Limited | Information & communication | 2010 |
| Jellybops Ltd | Wholesale & retail | 2013 |
| Jenner Road 1960 Limited | Extraterritorial | 2014 |
| Jermyn Doors and Windows Ltd | Construction | 2024 |
| Jetvantage Property Ltd | Real estate | 2026 |
| JFA Skin MED Limited | Health & social care | 2025 |
| JGR Aviation Ltd | Transport & logistics | 2020 |
| Jinko Chino Ltd | Wholesale & retail | 2024 |
| JJA Data & Security Ltd | Administrative & support | 2024 |
| Jjpm Construction Ltd | Construction | 2024 |
| Jjpm Landscaping Ltd | Administrative & support | 2026 |
| JK Recruitment Ltd | Administrative & support | 2016 |
| JKL Engineering Limited | Manufacturing | 2014 |
| JL Metals Ltd | Wholesale & retail | 2020 |
| JLL Consultancy Ltd | Arts & recreation | 2024 |
| JLL Developments Ltd | Construction | 2023 |
| JLO Financial Ltd | Professional & scientific | 2023 |
| JLP Electrical & Fire Ltd | Construction | 2014 |
| JMB Maintenance Limited | Construction | 2018 |
| JMS Property Maintenance Ltd | Construction | 2025 |
| Jncw Properties Ltd | Real estate | 2025 |
| JO Ferriday Medical Aesthetics Limited | Health & social care | 2017 |
| Joan Howe Limited | Professional & scientific | 2022 |
| Joel Sheppard Construction Services Limited | Construction | 2019 |
| John Churcher Electrical Ltd | Energy | 2011 |
| John Irvine Engineering Limited | Professional & scientific | 2016 |