| Imperial Consultancy Ltd | Information & communication | 2014 |
| Imperial Painting & Decorating Ltd | Construction | 2023 |
| Imperial Risk Solutions Limited | Professional & scientific | 2010 |
| Imperial Tiling London Ltd | Administrative & support | 2019 |
| Imperials Trader Limited | Hospitality | 2021 |
| Imperium Chambers (UK) Limited | Professional & scientific | 2021 |
| Impetus Education Solutions Limited | Education | 2007 |
| Imran AHD Limited | Wholesale & retail | 2017 |
| IMS Construction Limited | Construction | 2020 |
| IMS Freecrest Ltd | Construction | 2021 |
| IN HIM Possible Limited | Professional & scientific | 2017 |
| IN2FRUITION Limited | Professional & scientific | 2025 |
| Inbuilt Ltd | Real estate | 2025 |
| Incognito Paddington Limited | Hospitality | 2022 |
| Incognito Richmond Limited | Administrative & support | 2022 |
| Inconnect Ltd | Professional & scientific | 2003 |
| Independent Currencies Ltd | Professional & scientific | 2019 |
| Independent Insights Limited | Information & communication | 2020 |
| Independent Legal Assessors Ltd | Administrative & support | 2017 |
| Indigo Tango Software Limited | Information & communication | 2018 |
| Industrial Chemical Industries Limited | Extraterritorial | 2013 |
| Industrial Chemicals Group Limited | Manufacturing | 1976 |
| Industrial Chemicals Limited | Manufacturing | 1999 |
| Industrial Labour Limited | Administrative & support | 2018 |
| Industrial Maintenance Engineers (I.M.E.Contracts) Limited | Manufacturing | 1963 |
| Industrial Power Limited | Energy | 2016 |
| Infinite Lifestyle Management Ltd | Other services | 2024 |
| Infinity Capital Group Limited | Construction | 2020 |
| Infinity Estates and Homes Ltd | Real estate | 2021 |
| Infinity Wealth Consulting and Management Limited | Information & communication | 2020 |
| Inflatabar Limited | Hospitality | 2012 |
| Infogaps Limited | Information & communication | 2024 |
| Information Technology Rentals Limited | Administrative & support | 2000 |
| ING Construction Limited | Construction | 2007 |
| ING Solar Limited | Extraterritorial | 2007 |
| Ingatestone Estates Limited | Real estate | 2025 |
| Ingen Technology Limited | Information & communication | 2017 |
| Ingenious Air Ltd | Extraterritorial | 2013 |
| Ingenious Probiotics Ltd | Wholesale & retail | 2018 |
| Ingness Facilities Management Ltd | Construction | 2026 |
| Ingram Lettings Ltd | Real estate | 2026 |
| Ingrave Community Association | Health & social care | 2004 |
| Initiate Resourcing Limited | Administrative & support | 2018 |
| INK Digital Ltd | Professional & scientific | 2019 |
| Inka Holdings (UK) Limited | Real estate | 2002 |
| Inka Presswood Pallets Limited | Wholesale & retail | 1984 |
| Inkaholics Limited | Other services | 2014 |
| Inline Removals & Storage Limited | Transport & logistics | 2005 |
| Inneo Limited | Administrative & support | 2005 |
| Inneo Recruitment Ltd | Extraterritorial | 2015 |
| Inner City Waste Management Ltd | Water & waste | 2017 |
| Innovation Construction and Development Ltd | Construction | 2018 |
| Innovation Management Development (UK) Limited | Professional & scientific | 2004 |
| Innquire Ltd | Information & communication | 2026 |
| Inotegrity Holdings Limited | Financial services | 2024 |
| Inside OUT Recruitment Limited | Administrative & support | 2001 |
| Inside Plus Ltd | Construction | 2010 |
| Inspace Media Ltd | Manufacturing | 2018 |
| Inspinn Ltd | Information & communication | 2018 |
| Inspire Installations Ltd | Administrative & support | 2018 |
| Inspire Minds Through Sports Ltd | Health & social care | 2018 |
| Inspire Minds Together CIC | Education | 2026 |
| Instant Despatch Services Limited | Transport & logistics | 2002 |
| Instant Golf Holidays Limited | Administrative & support | 2025 |
| Insurance Watch Services Limited | Extraterritorial | 1997 |
| Insync Consulting Limited | Professional & scientific | 2026 |
| Intaprojects Limited | Extraterritorial | 2011 |
| Intaprojects Ventures Ltd | Professional & scientific | 2024 |
| Integra Finance Ltd | Financial services | 2006 |
| Integral Controls Ltd | Construction | 2022 |
| Integral Corporation Limited | Financial services | 2025 |
| Integral Properties Limited | Construction | 2025 |
| Integration Data Services Limited | Information & communication | 2016 |
| Integrator World Ltd | Administrative & support | 2025 |
| Integrity Car Sales Limited | Wholesale & retail | 2015 |
| Integrity Insurance Brokers Limited | Extraterritorial | 2001 |
| Intellectual Homes Ltd | Real estate | 2023 |
| Intellectual Solutions Ltd | Information & communication | 2005 |
| Intelligent Health Advances Limited | Health & social care | 2016 |
| Intelligent Working Ltd | Information & communication | 1995 |
| Interact Communications Limited | Information & communication | 2008 |
| Interact Marketing Services Limited | Manufacturing | 1976 |
| Interact Technology Ltd | Information & communication | 2007 |
| Interesting Ventures Ltd | Professional & scientific | 2021 |
| Interexpres Ltd | Transport & logistics | 2018 |
| International Chandeliers Ltd | Administrative & support | 2021 |
| International Freight Network Limited | Transport & logistics | 2018 |
| International Systems and Communications Limited | Information & communication | 1991 |
| Intertek Capital Resources Limited | Financial services | 1999 |
| Intertek Certification Limited | Administrative & support | 1986 |
| Intertek Finance NO. 2 Ltd | Financial services | 2012 |
| Intertek Finance PLC | Financial services | 1996 |
| Intertek Global (Iraq) Limited | Administrative & support | 2014 |
| Intertek Holdings Limited | Professional & scientific | 2002 |
| Intertek Inspection Services UK Limited | Administrative & support | 1969 |
| Intertek International Limited | Administrative & support | 1906 |
| Intertek Medical Notified Body UK Limited | Professional & scientific | 2022 |
| Intertek Nominees Limited | Professional & scientific | 2003 |
| Intertek Overseas Holdings Limited | Professional & scientific | 1952 |
| Intertek Quality Services Ltd | Extraterritorial | 1991 |