| Injuna Ltd | Professional & scientific | 2025 |
| INK Port Tattoos Ltd | Other services | 2026 |
| INK Realm Ltd | Arts & recreation | 2025 |
| Inkelle Ltd | Professional & scientific | 2026 |
| Inman's Electricals Ltd | Construction | 2022 |
| Inmark Ltd | Wholesale & retail | 2012 |
| Inner YOU Counselling Ltd | Health & social care | 2024 |
| INNOV8 Academy Limited | Education | 2025 |
| INNOV8 Sportz C.I.C. | Arts & recreation | 2012 |
| Innovais Ltd | Manufacturing | 2020 |
| Innovare Strategic Solutions Ltd | Hospitality | 2025 |
| Innovate 2 Elevate Ltd | Professional & scientific | 2023 |
| Innovate 22 Limited | Professional & scientific | 2022 |
| Innovate UK Loans Limited | Financial services | 2018 |
| Innovation IT Support Ltd | Information & communication | 2010 |
| Innovative Knitex International Ltd | Wholesale & retail | 2023 |
| Innovay Consulting Ltd | Professional & scientific | 2025 |
| Innovest Software Limited | Information & communication | 2020 |
| Innovision Audit Solutions Limited | Professional & scientific | 2024 |
| Innowhizz Ltd | Information & communication | 2015 |
| Insideout Improvements Ltd | Construction | 2024 |
| Insight Partner Solutions Ltd | Professional & scientific | 2024 |
| Insight Retail Risk Consultancy Ltd | Professional & scientific | 2015 |
| Insightful Transformation Ltd | Professional & scientific | 2021 |
| Inspirat Consultancy Limited | Professional & scientific | 2018 |
| Inspiration Training Ltd | Education | 2019 |
| Inspirational Bathrooms (Chippenham) Ltd | Wholesale & retail | 2015 |
| Inspiratus Senior Care Limited | Health & social care | 2012 |
| Inspire Enrichment CIC | Education | 2025 |
| Inspire Hair & Beauty (Swindon) Limited | Other services | 2013 |
| Inspire Studios Media Ltd | Information & communication | 2021 |
| Inspired Bespoke Cabinetry & Joinery Ltd | Construction | 2022 |
| Inspired Garage Doors and Maintenance Ltd | Construction | 2015 |
| Inspired Tours Ltd | Administrative & support | 2026 |
| Installid Limited | Extraterritorial | 1994 |
| Institute for the Management of Information Systems | Other services | 1974 |
| Insynergy Marketing Ltd | Information & communication | 2017 |
| Insysdata Ltd | Information & communication | 2013 |
| Intecforce Ltd | Information & communication | 2019 |
| Intechnic Ltd | Wholesale & retail | 2013 |
| Integral Sourcing Operation Limited | Other services | 2005 |
| Integrated Digital Ltd | Information & communication | 2021 |
| Integrated Health and Care Solutions Ltd | Professional & scientific | 2017 |
| Integrating Rail Infrastructure Solutions Ltd | Professional & scientific | 2024 |
| Integris IT Solutions Ltd | Professional & scientific | 2025 |
| Intellect Testing Consultancy Limited | Information & communication | 2012 |
| Intelligenbio Ltd | Professional & scientific | 2026 |
| Intelligent Dialogue Limited | Professional & scientific | 2006 |
| Inter Car Clearing Limited | Administrative & support | 2025 |
| Interactions Limited | Professional & scientific | 1999 |
| Interchange Research Ltd | Professional & scientific | 2019 |
| Interconnect Technology Ltd | Professional & scientific | 2022 |
| Interfaces Engineering Limited | Information & communication | 2017 |
| Intergraph (UK) Limited | Information & communication | 1979 |
| Intermach Engineering Limited | Manufacturing | 1997 |
| International Bodyguard Associates Ltd | Administrative & support | 2006 |
| International Business Logistics Limited | Administrative & support | 1992 |
| International Greenkeepers for Hire Ltd | Education | 2022 |
| International Human Resources Management Limited | Other services | 2009 |
| International Merchant Capital Limited | Extraterritorial | 2014 |
| International School of Veterinary Postgraduate Studies Limited | Professional & scientific | 2020 |
| International Taekwon-Do Federation Limited | Education | 2009 |
| Intersec Limited | Information & communication | 2019 |
| Inthedetail Competitions Limited | Wholesale & retail | 2024 |
| Intrepid Design Associates Limited | Administrative & support | 2009 |
| Intuiti Solutions Ltd | Professional & scientific | 2012 |
| Inuti Interiors Ltd | Professional & scientific | 2024 |
| Inventor Club Ltd | Education | 2023 |
| Invenue Ltd | Administrative & support | 2021 |
| Investax Consulting Ltd | Professional & scientific | 2017 |
| Investax Management LLP | | 2006 |
| Investment Reporting Technologies Ltd | Information & communication | 2023 |
| Invicta Surveys Limited | Professional & scientific | 2007 |
| Inyeon Cosmetics Ltd | Wholesale & retail | 2026 |
| IO IT Ltd | Information & communication | 2012 |
| Ioansuci Limited | Transport & logistics | 2018 |
| Ionela Healthcare Ltd | Health & social care | 2018 |
| Ionic Cleaning Systems Limited | Extraterritorial | 2016 |
| Ionic Filter Systems Limited | Extraterritorial | 2016 |
| Ionic Systems Limited | Manufacturing | 1991 |
| IOT Management Consultancy Limited | Professional & scientific | 2017 |
| Iotechnix Limited | Professional & scientific | 2015 |
| Ipft Ltd | Education | 2023 |
| Ipona IP LLP | | 2009 |
| Iprovefit Living Ltd | Health & social care | 2013 |
| IQ Automations Solutions Ltd | Information & communication | 2024 |
| Iqbix Ltd | Professional & scientific | 2017 |
| Irina Pepenel Ltd | Transport & logistics | 2018 |
| Iris Parsons Ltd | Health & social care | 2022 |
| Irish Fairy Tails Ltd | Wholesale & retail | 2025 |
| Iroma Ltd | Extraterritorial | 2024 |
| Iron Ring Capital Ltd | Financial services | 2025 |
| IRON27 Ltd | Wholesale & retail | 2025 |
| IRT Aviation Ltd | Education | 2019 |
| Isaac & Asher Properties Ltd | Real estate | 2024 |
| Isaac Oguns Care Ltd | Health & social care | 2015 |
| Isaac OS GAS Services Ltd | Construction | 2025 |
| Isaackayode Ltd | Health & social care | 2023 |
| Iscape Ltd. | Manufacturing | 1999 |
| Iseri Investments Ltd | Real estate | 2023 |