| Impact Design & Print Ltd | Manufacturing | 1996 |
| Impact Growth Partnership Ltd | Information & communication | 2026 |
| Impact Moling Trenchless Installations Limited | Construction | 2006 |
| Impact Teamwear Ltd | Manufacturing | 2026 |
| Imperial Building and Landscapes Limited | Administrative & support | 2016 |
| Imperium Tax and Accounting Limited | Professional & scientific | 2021 |
| Impress Cars Ltd | Wholesale & retail | 2019 |
| IMW Tours Ltd | Administrative & support | 2016 |
| Imya Ltd | Health & social care | 2024 |
| IN2CREATIVE Limited | Professional & scientific | 2015 |
| Inauctus Private Limited | Information & communication | 2025 |
| Inayit Ltd | Information & communication | 2024 |
| Inca Roots Hair Specialists Ltd | Other services | 2025 |
| INCEPTION2 Ltd | Other services | 2016 |
| Inclusion Quality Mark (UK) Limited | Education | 2011 |
| Inclusion Quality Mark Limited | Education | 2016 |
| Incredible U.K. Ltd | Wholesale & retail | 2025 |
| Incubateit Ltd | Wholesale & retail | 2021 |
| Independent Chauffeur Service Ltd | Other services | 2011 |
| Indigo & Otis Ltd | Wholesale & retail | 2023 |
| Indigo Chimp Limited | Professional & scientific | 2017 |
| Inductoheat Banyard Limited | Manufacturing | 1967 |
| Inductoheat Europe Limited | Manufacturing | 1982 |
| Inductotherm Heating & Welding Limited | Manufacturing | 1971 |
| Ines Swan Ltd | Other services | 2025 |
| Infinite Images Limited | Professional & scientific | 2019 |
| Infisim Limited | Information & communication | 2016 |
| Infosec Matters Ltd | Administrative & support | 2016 |
| Infosum Limited | Information & communication | 2015 |
| ING Decor Ltd | Construction | 2018 |
| Ingenious Quality Ltd | Professional & scientific | 2005 |
| Ingrams Automotive and Fabrications Ltd | Wholesale & retail | 2022 |
| Inhouse Bookkeeping Ltd | Professional & scientific | 2025 |
| Initial Finance Limited | Financial services | 2009 |
| Inkirudigital Limited | Wholesale & retail | 2026 |
| Inmedio Logistik Ltd | Transport & logistics | 2016 |
| Innit Drink Ltd | Manufacturing | 2025 |
| Inno Support Limited | Health & social care | 2018 |
| Innofootball Limited | Education | 2025 |
| Innogen Technologies Ltd | Information & communication | 2012 |
| Innovation Control Limited | Construction | 1997 |
| Innovavia Limited | Transport & logistics | 2023 |
| Inquis Accountants Limited | Professional & scientific | 2019 |
| Inside Office Consultancy Ltd | Professional & scientific | 2019 |
| Inside OUT Pavilion Ltd | Extraterritorial | 2021 |
| Insight Parenting Ltd | Information & communication | 2009 |
| Insight Support 24 Ltd | Real estate | 2024 |
| Insignia Medical Systems Limited | Information & communication | 1999 |
| Inspero | Other services | 2012 |
| Inspire Land Consultants Limited | Real estate | 2026 |
| Inspire Property Consultants Ltd | Real estate | 2025 |
| Inspired by Design Building Limited | Professional & scientific | 2022 |
| Inspired Fitness Training Ltd | Arts & recreation | 2010 |
| Inspired Focus Ltd | Professional & scientific | 2025 |
| Inspired Workspaces Ltd | Manufacturing | 2019 |
| Instavolt Limited | Energy | 2016 |
| Instinct Sports Limited | Manufacturing | 2015 |
| Insurtech Solutions Ltd | Information & communication | 2022 |
| Integrated Minds Psychology Ltd | Health & social care | 2026 |
| Integritech Consultancy Ltd | Administrative & support | 2024 |
| INTEGRO360 Ltd | Information & communication | 2018 |
| Intelligent Data Systems (UK) Limited | Information & communication | 2004 |
| Intelligent Waste Management Limited | Administrative & support | 2011 |
| INTENT4 Ltd | Financial services | 2018 |
| Interactive Applications Limited | Information & communication | 2011 |
| Intercity Electrical Ltd | Construction | 2022 |
| Intercompany Mediation Limited | Extraterritorial | 2011 |
| Interconics Limited | Manufacturing | 1987 |
| Interested Vests Ltd | Real estate | 2021 |
| International Foundation for Muslim Theology (Ifmt) | Administrative & support | 2018 |
| International Inclusion Quality Mark Limited | Education | 2012 |
| Internationoil Limited | Extraterritorial | 2008 |
| Interrupt Labs (Australia) Limited | Information & communication | 2022 |
| Interrupt Labs (US) Limited | Information & communication | 2022 |
| Interrupt Labs Holdings Limited | Financial services | 2024 |
| Interrupt Labs Limited | Information & communication | 2021 |
| Intersett Block Paving Ltd | Construction | 2025 |
| Intersett Paving UK Limited | Construction | 2020 |
| Interweave NOW Limited | Professional & scientific | 2008 |
| Intrapsyche Ltd | Health & social care | 2022 |
| Inventor Smart Care Ltd | Wholesale & retail | 2020 |
| Investment Oracle Limited | Information & communication | 2018 |
| Involvo Limited | Information & communication | 2020 |
| Ionix Development Company Limited | Extraterritorial | 1980 |
| IP Cleaning Services Ltd | Administrative & support | 2021 |
| IP World Solutions Ltd | Information & communication | 2019 |
| IPC Renervation Services Ltd | Construction | 2025 |
| Iplumb Heating Services Ltd | Construction | 2010 |
| IPV Trans Ltd | Transport & logistics | 2019 |
| Iqblade Limited | Information & communication | 2019 |
| Iqrf UK Limited | Manufacturing | 2019 |
| Iridium Systems Ltd | Information & communication | 2014 |
| Irispoint Investments Limited | Real estate | 2025 |
| Ironclad Properties Ltd | Real estate | 2026 |
| IRQ Group Limited | Financial services | 2024 |
| Island Court Care Home Limited | Health & social care | 2019 |
| Island-Bis Ltd | Health & social care | 2026 |
| Isolevel Ltd | Real estate | 2014 |
| Isrp Ltd | Transport & logistics | 2024 |
| Istanbul Dursun Barbers Limited | Other services | 2026 |