| Infinite IT Solutions Ltd | Information & communication | 2010 |
| Infinite Smart Tech Limited | Information & communication | 2026 |
| Inform Financial Solutions Limited | Financial services | 2025 |
| Information Printing Technology Limited | Manufacturing | 2002 |
| Inovacia Limited | Manufacturing | 2017 |
| Inqubator Ltd | Education | 2011 |
| Insidetech Ltd | Information & communication | 2018 |
| Inspire 2 Ignite CIC | Education | 2022 |
| Inspired Football Academy Limited | Education | 2020 |
| Instant Home Limited | Administrative & support | 2000 |
| Intalyo Trading AS Fabrikraft UK Ltd | Wholesale & retail | 2004 |
| Integra Accountants Limited | Professional & scientific | 2024 |
| Integra AG Ltd | Professional & scientific | 2021 |
| Integraltik Ltd | Other services | 2023 |
| Integrated Pathway Solutions Limited | Administrative & support | 2019 |
| Interim Project Finance Limited | Professional & scientific | 2014 |
| Interinvest Global Ltd | Administrative & support | 2012 |
| International Association of Social Media Professionals | Professional & scientific | 2017 |
| Invecon International Ltd | Professional & scientific | 2020 |
| Invisible World Limited | Information & communication | 2000 |
| Iolite Pharma Consulting Limited | Professional & scientific | 2010 |
| ION Creative Harrogate Limited | Professional & scientific | 2012 |
| ION Lebedenco Ltd | Construction | 2014 |
| Iplasma Limited | Professional & scientific | 2021 |
| Irised Ltd | Other services | 2022 |
| IRM Consulting Ltd | Administrative & support | 2023 |
| Istsno Ltd | Hospitality | 2025 |
| Ives & Company Limited | Information & communication | 1998 |
| Izod Lime Plastering Ltd | Construction | 2025 |
| Izzol Ltd | Other services | 2018 |
| J & LS Property Ltd | Construction | 2020 |
| J Bros Properties Limited | Real estate | 2025 |
| J C Ellerton Painting and Decorating Limited | Administrative & support | 2017 |
| J C General Builders Ltd | Construction | 2021 |
| J Jordan Surfacing Ltd | Professional & scientific | 2026 |
| J Kelly Logistics Ltd | Transport & logistics | 2011 |
| J P Godfrey Limited | Professional & scientific | 2013 |
| J. Ashton and Co. (Electrical) Limited | Construction | 1988 |
| J.H. Computer Consultants Ltd | Information & communication | 1992 |
| Jabula Interior Projects Ltd | Construction | 2009 |
| Jacaranda Tree Enterprise Ltd | Hospitality | 2025 |
| Jack Charles Contracting Services Ltd | Other services | 2025 |
| Jack's Live Lounges Ltd | Hospitality | 2022 |
| Jack's Private Hire Ltd | Transport & logistics | 2019 |
| Jacksons Solutions Ltd | Construction | 2018 |
| Jacob Graff Limited | Wholesale & retail | 2000 |
| Jamber Properties (Commercial) Ltd | Real estate | 2024 |
| James Elder Plumbing & Heating Ltd | Construction | 2023 |
| James Whish Ltd | Construction | 2024 |
| Jane Webber Orthopaedics Ltd | Health & social care | 2020 |
| Jarek Trans Limited | Transport & logistics | 2012 |
| JB Music & Events Ltd | Arts & recreation | 2026 |
| JB Site Fabrications & Services Limited | Manufacturing | 2018 |
| JCW Welding and Fabrication Services Limited | Manufacturing | 2014 |
| JD Contractors Ltd | Construction | 2021 |
| Jeluma Labs Ltd | Information & communication | 2025 |
| Jemima House Day Nursery Ltd | Education | 2024 |
| Jensaria Ltd | Real estate | 2026 |
| JET Rental Management Ltd | Real estate | 2024 |
| JEZ Guyanese Cuisine Ltd | Wholesale & retail | 2023 |
| JG Instruction Ltd | Health & social care | 2016 |
| JHC Software Limited | Information & communication | 2005 |
| Jim's Coffee Shop Buckden Limited | Hospitality | 2026 |
| JJ Flat Roofing Ltd | Construction | 2024 |
| JJL Kitchens Limited | Construction | 2022 |
| JJP Transport Ltd | Water & waste | 2025 |
| JLG Design (Commercial) Limited | Administrative & support | 2016 |
| John Izod Limited | Construction | 2006 |
| Jolio Ltd | Construction | 2013 |
| JON Aaron Green Photography Limited | Professional & scientific | 2023 |
| Joule Investments Ltd | Financial services | 2026 |
| Jovel Supply Limited | Wholesale & retail | 2024 |
| Jozef Kitchen Ltd | Hospitality | 2024 |
| JPA Construction Ltd | Construction | 2019 |
| JRN Building Services Limited | Construction | 2006 |
| JRN Holdings Group Ltd | Financial services | 2024 |
| JRN Painting and Decorating Ltd | Construction | 2024 |
| JRZ Electronics Ltd | Professional & scientific | 2014 |
| JSS Heating & Plumbing Ltd | Construction | 2024 |
| JT Convenience Stores Limited | Wholesale & retail | 2018 |
| JT Stores Ltd | Wholesale & retail | 2026 |
| Jtreferbishments Ltd | Real estate | 2024 |
| JUDG3D Limited | Real estate | 2014 |
| Juicy Records Ltd | Information & communication | 2021 |
| JUM Services Ltd | Hospitality | 2021 |
| Juniper Trading Group Ltd | Professional & scientific | 2019 |
| Just Health Limited | Health & social care | 2013 |
| JY Asset Investment Co Ltd | Other services | 2023 |
| K and P Builders Limited | Construction | 2023 |
| K Fisk Plumbing & Heating Limited | Construction | 2009 |
| K&L Tech Ltd | Wholesale & retail | 2020 |
| K&R Building Services Limited | Construction | 2023 |
| Kaaspi Limited | Administrative & support | 2020 |
| Kadio Ltd | Other services | 2022 |
| Kaio Marketing Ltd | Professional & scientific | 2021 |
| Kaliveri Ltd | Other services | 2021 |
| Kallio Ltd | Professional & scientific | 2024 |
| Kamara Holdings Limited | Financial services | 2019 |
| Kaocuk Ltd | Wholesale & retail | 2022 |
| KAS Heating and Plumbing Limited | Construction | 2018 |