| Inline Scaffolding Bucks Ltd | Construction | 2013 |
| Innergraph Limited | Information & communication | 2007 |
| Innertuition Coaching and Consulting Ltd | Professional & scientific | 2007 |
| Innisoutcome Ltd | Professional & scientific | 2025 |
| Innograe Limited | Professional & scientific | 2015 |
| Innojewels Ltd | Wholesale & retail | 2025 |
| Innosight Tech Ltd | Information & communication | 2024 |
| Innovation Landscape and Design Ltd | Administrative & support | 2024 |
| Innovert Consulting Ltd | Professional & scientific | 2018 |
| Inoia Limited | Information & communication | 2018 |
| Inoni Group Limited | Professional & scientific | 2002 |
| Inoni Limited | Information & communication | 2005 |
| Inside Edge Sports Consulting Ltd | Professional & scientific | 2017 |
| Inside Outside Kitchens & Bathrooms Limited | Construction | 2007 |
| Insight Aiming Ltd | Education | 2016 |
| Inspire Interiors Ltd | Construction | 2025 |
| Insta (International) Limited | Professional & scientific | 2014 |
| Insta Coustic Limited | Construction | 1987 |
| Insta Group Holdings Limited | Professional & scientific | 1988 |
| Instaclad Limited | Extraterritorial | 2012 |
| Instafloor Limited | Extraterritorial | 2012 |
| Instagen Limited | Extraterritorial | 2012 |
| Instaproperty Limited | Professional & scientific | 1988 |
| Instatyres Ltd | Wholesale & retail | 2025 |
| Instinct Marketing Ltd | Professional & scientific | 2024 |
| Insynq Limited | Administrative & support | 2014 |
| Inteam Limited | Professional & scientific | 2009 |
| Integic Ltd | Information & communication | 2026 |
| Integrated Specialist Services Ltd | Administrative & support | 2019 |
| Integrated Specialist Systems Limited | Construction | 2000 |
| Integriai Limited | Information & communication | 2025 |
| Intellegis Ltd | Administrative & support | 2018 |
| Intelligent Program Manager Limited | Information & communication | 2021 |
| Intenex Ltd | Information & communication | 2022 |
| Interactive Advertising Limited | Information & communication | 1995 |
| Intercase UK Limited | Information & communication | 2001 |
| Interim IT Sales Limited | Professional & scientific | 2013 |
| Interior Doors Ltd | Wholesale & retail | 2024 |
| Interiors Fixing Ltd | Construction | 2017 |
| Intermarketing Agency Limited | Professional & scientific | 1988 |
| Intermarketing Group Limited | Professional & scientific | 2011 |
| International Handling Ltd | Water & waste | 2019 |
| Intuitive Surgical Limited | Administrative & support | 2008 |
| Inuvi Diagnostics Limited | Professional & scientific | 2018 |
| Inuvi Group Limited | Financial services | 2019 |
| Inuvi Health Limited | Health & social care | 2013 |
| Inuvi Medical Services Limited | Financial services | 2019 |
| Invaluable Things Ltd | Wholesale & retail | 2019 |
| Invartis Consulting (UK & Europe) Limited | Professional & scientific | 2018 |
| Invenio Business Solutions Investment Limited | Information & communication | 2020 |
| Invenio Business Solutions Limited | Information & communication | 2006 |
| Inventus Group Holdings Limited | Financial services | 2025 |
| Inventus Group Ltd | Information & communication | 2020 |
| Inventus Limited | Administrative & support | 2022 |
| Inventus Mobile Limited | Administrative & support | 2022 |
| Inwards Limited | Administrative & support | 1999 |
| Ioema Fibre Limited | Construction | 2023 |
| Ipsecpro Ltd | Information & communication | 2011 |
| Iraye Limited | Wholesale & retail | 2021 |
| IRO Consultancy Ltd | Professional & scientific | 2024 |
| Iroko Solutions Ltd | Information & communication | 2024 |
| Ironburg Inventions Limited | Professional & scientific | 2011 |
| Irvin Bros. (Fleet Works) Limited | Real estate | 1963 |
| Ishan Estates Ltd | Real estate | 2025 |
| Ishi Projects Ltd | Professional & scientific | 2014 |
| Island Time Limited | Information & communication | 2022 |
| Isometric 3D Ltd | Information & communication | 2022 |
| Isotope Music Limited | Wholesale & retail | 2013 |
| Isport Ltd | Information & communication | 2019 |
| Istari Investment Partners LLP | | 2010 |
| IT RJC Ltd | Information & communication | 2018 |
| IT Support Solutions Ltd | Information & communication | 2008 |
| It's the Little Things Ltd | Wholesale & retail | 2022 |
| ITS ALL About YOU Ltd | Administrative & support | 2014 |
| ITS Logistics Ltd | Wholesale & retail | 2015 |
| ITS Pizza Time Ltd | Hospitality | 2026 |
| ITS Pizzas Time Ltd | Hospitality | 2022 |
| Itus Limited | Information & communication | 2012 |
| Ivar's Ventures Ltd | Real estate | 2024 |
| IVM Engineering Limited | Manufacturing | 2018 |
| IWD Renovations Ltd | Construction | 2025 |
| Ixal Ltd | Professional & scientific | 2011 |
| J & L Capital Ltd | Real estate | 2024 |
| J & R Fabrications Limited | Manufacturing | 2003 |
| J a S Sekhon Johal Properties Limited | Real estate | 2026 |
| J and P Carpentry Limited | Construction | 2012 |
| J Bandy Consulting Ltd | Professional & scientific | 2015 |
| J Bees Electrics Ltd | Construction | 2021 |
| J D Cleaning Services Limited | Administrative & support | 2009 |
| J F Page Ltd | Real estate | 2015 |
| J G Property Management Limited | Real estate | 2003 |
| J Hankin Holdings Ltd | Education | 2024 |
| J Jennings Scenery Limited | Construction | 2022 |
| J K Bathrooms Limited | Wholesale & retail | 2007 |
| J Newman Services Limited | Construction | 2026 |
| J Ward Joint Sealing Specialists Ltd | Construction | 2015 |
| J&D Chalk Holdings Limited | Hospitality | 2026 |
| J. Chaffey Electrical Ltd | Construction | 2022 |
| J.Downes Estates Ltd | Real estate | 2025 |
| J.H. Strategic Planning Limited | Professional & scientific | 2015 |