| Instructor & Examiner Academy Ltd | Education | 2019 |
| Instrumentation Consulting Services Limited | Professional & scientific | 2012 |
| Insulwatt Limited | Manufacturing | 2007 |
| Insurance GPS Services Ltd | Financial services | 2018 |
| Insurance Helpline Ltd | Financial services | 2018 |
| Insycloud Limited | Wholesale & retail | 2023 |
| Insync Corporate Healthcare Limited | Health & social care | 2006 |
| Insync Healthcare Pharmacy Limited | Wholesale & retail | 2006 |
| Intamed Ltd | Administrative & support | 2024 |
| Intandem Architecture Ltd | Professional & scientific | 2023 |
| Intapeople Group Limited | Financial services | 2019 |
| Intapeople Limited | Information & communication | 1994 |
| Intatherm (Cardiff) Ltd | Professional & scientific | 2017 |
| Intech Systems Ltd | Other services | 2017 |
| Inted Interiors Limited | Construction | 2016 |
| Integra Innovations Ltd | Construction | 2024 |
| Integra Marketing Ltd | Professional & scientific | 2020 |
| Integra Pharma Consulting Ltd | Professional & scientific | 2026 |
| Integral Blinds Ltd | Manufacturing | 2010 |
| Integral Cataract and Retinal Surgery Limited | Health & social care | 2026 |
| Integral Procurement Solutions Limited | Professional & scientific | 2014 |
| Integrale-It Ltd | Information & communication | 2014 |
| Integrated BMS Solutions Limited | Information & communication | 2017 |
| Integrated Business Corporation Ltd | Professional & scientific | 2021 |
| Integrated Certification Solutions Ltd | Professional & scientific | 2015 |
| Integrated Comfort Systems Ltd | Construction | 2022 |
| Integrated Energy Infrastructure Limited | Energy | 2025 |
| Integrated Food Ingredients Ltd | Wholesale & retail | 2026 |
| Integrated Powertech Limited | Manufacturing | 2021 |
| Integrated Response Limited | Professional & scientific | 2015 |
| Integrated Systems Group Ltd | Construction | 2020 |
| Integrated Visual Arts Ltd | Professional & scientific | 2026 |
| Integrity Automotive Solutions Limited | Wholesale & retail | 2017 |
| Integrity Group Solutions Limited | Administrative & support | 2020 |
| Integrity Payment UK Ltd | Administrative & support | 2018 |
| Integrity Training (WBL) Limited | Professional & scientific | 2013 |
| INTEGRUM7 Limited | Professional & scientific | 2021 |
| Intek Floors Limited | Wholesale & retail | 1981 |
| Intelact Ltd | Administrative & support | 2025 |
| Intelguards Ltd | Information & communication | 2025 |
| Intelitesting Ltd | Information & communication | 2021 |
| Intellas UK Ltd | Information & communication | 2009 |
| Intelle Infrastructure Limited | Administrative & support | 2021 |
| Intellect HR Ltd | Administrative & support | 2017 |
| Intellectiq Innovations Ltd | Wholesale & retail | 2024 |
| Intellectual Constructs Ltd | Construction | 2019 |
| Intelli-Eye Monitoring and Cctv Installation Limited | Administrative & support | 2015 |
| Intelligent Capital Investments Ltd | Financial services | 2022 |
| Intelligent Education Systems Ltd | Information & communication | 2024 |
| Intelligent Financing (Holdings) Limited | Financial services | 2022 |
| Intelligent Financing Limited | Financial services | 2010 |
| Intelligent Goalkeeping Ltd | Education | 2022 |
| Intelligent I.T. Solutions Limited | Information & communication | 2005 |
| Intelligent Imagination Ltd | Information & communication | 2019 |
| Intelligent Information Technology Services Limited | Wholesale & retail | 2018 |
| Intelligent IP Ltd | Information & communication | 2026 |
| Intelligent PMO Limited | Professional & scientific | 2022 |
| Intelligent Ultrasound Limited | Information & communication | 2012 |
| Intelligenz Limited | Information & communication | 2019 |
| Intellitag Limited | Information & communication | 2016 |
| Intension (UK) Limited | Manufacturing | 1972 |
| INTENT360 Ltd | Information & communication | 2024 |
| Inter Property Services Limited | Construction | 2014 |
| Inter-Aid (Cardiff) Limited | Wholesale & retail | 1992 |
| Interactive Engineering Ltd | Manufacturing | 2011 |
| Interactive Fitness Limited | Manufacturing | 1993 |
| Interactivename Ltd | Information & communication | 2023 |
| Interate Shipping and Trading PC | | 2020 |
| Interbridge Mortgages Holdings Limited | Financial services | 2023 |
| Interbridge Mortgages Limited | Financial services | 2023 |
| Interburns Limited | Health & social care | 2007 |
| Intercars Ltd. | Wholesale & retail | 2015 |
| Intercity Removals Limited | Transport & logistics | 2015 |
| Intercontinental Cooparation Ltd | Manufacturing | 2021 |
| Intercultural Exchange Ltd | Education | 2023 |
| Interequiprent Limited | Administrative & support | 2025 |
| Interface-Metrix Ltd | Professional & scientific | 2016 |
| Interflowe Limited | Information & communication | 2017 |
| Interior Design Evolution Ltd | Education | 2025 |
| Interior Makes Ltd | Professional & scientific | 2026 |
| Interiors by Harry Ltd | Professional & scientific | 2018 |
| Interlagos Holdings Limited | Hospitality | 2017 |
| Interlet Group Ltd | Real estate | 2020 |
| Interlink Technology Limited | Real estate | 2021 |
| Interlink Venter Ltd | Wholesale & retail | 2020 |
| Interludee Ltd | Hospitality | 2018 |
| Intermarine UK Group Holdings Limited | Financial services | 2024 |
| Intermarine UK Limited | Professional & scientific | 2009 |
| International Academy for Consulting and Training (Consultancy) Ltd | Professional & scientific | 2020 |
| International Academy for Leadership and Management Ltd | Professional & scientific | 2025 |
| International Academy of Billiards, Snooker and Mind Games Ltd | Education | 2024 |
| International Academy of Chinese Culinary Arts Ltd | Education | 2019 |
| International Action Learning (UK) Association | Extraterritorial | 2019 |
| International Ades College Ltd | Education | 2025 |
| International Baccalaureate Fund (UK) | Education | 2008 |
| International Baccalaureate Organization (UK) Limited | Administrative & support | 2008 |
| International Business Press Ltd | Information & communication | 2014 |
| International Business Solutions Ltd | Wholesale & retail | 2016 |
| International Cash Car Ltd | Wholesale & retail | 2025 |
| International Centre for Aerospace Training Limited | Education | 2006 |