| IBS Lettings Ltd | Real estate | 2020 |
| Ibuild Incorporated Ltd | Real estate | 2020 |
| Ibuild Property Limited | Real estate | 2021 |
| IC Drywall Ltd | Construction | 2025 |
| IC Engineering Ltd | Professional & scientific | 2023 |
| IC Plumbing Ltd | Construction | 2025 |
| ICA Engineering Ltd | Professional & scientific | 2026 |
| ICB Global Trade Ltd | Wholesale & retail | 2025 |
| ICD Consulting Limited | Professional & scientific | 2016 |
| ICD Control Services Limited | Professional & scientific | 2013 |
| ICD Management Services Ltd | Financial services | 2010 |
| Ice Blasters Ltd | Administrative & support | 2021 |
| Ice Plastering Limited | Construction | 2003 |
| Ice Roofing & Cladding Limited | Construction | 2017 |
| Ice Trustees Limited | Other services | 2021 |
| Iceberg Properties Limited | Real estate | 2020 |
| Iced Spray Coatings Ltd | Construction | 2025 |
| Icehaus Limited | Construction | 2010 |
| Icena Ltd | Professional & scientific | 2019 |
| Iceni Construction (Norwich) Limited | Extraterritorial | 2020 |
| Iceni Worldwide Ltd | Education | 2021 |
| ICF Premier Ltd | Construction | 2021 |
| Icgg Ltd | Construction | 2024 |
| Ichnolites Limited | Financial services | 2019 |
| Icic Holdings Ltd | Transport & logistics | 2023 |
| Iclean 4SELFCAR Ltd | Wholesale & retail | 2025 |
| Iclean Solution Cleaning Contractor Ltd | Administrative & support | 2023 |
| Icomm Communications Limited | Manufacturing | 2013 |
| Icomm Solutions Limited | Information & communication | 2026 |
| Icon Dental Installations Ltd | Construction | 2019 |
| Icon Hosiery Limited | Wholesale & retail | 2006 |
| Iconia (London) Ltd | Households | 2008 |
| Icons Barbers Ltd | Other services | 2018 |
| Icons Group Ltd | Health & social care | 2018 |
| Icreate Events Ltd | Administrative & support | 2023 |
| ICS Express Limited | Transport & logistics | 2015 |
| Icsm Ltd | Administrative & support | 2019 |
| Icube Capitol Limited | Information & communication | 2025 |
| ICV Trans Logistics Ltd | Transport & logistics | 2023 |
| Icvl Ltd | Professional & scientific | 2024 |
| ID Brickwork Ltd | Construction | 2023 |
| ID Card Centre Limited | Information & communication | 2011 |
| ID4K9 Ltd | Other services | 2024 |
| IDA Development Ltd | Construction | 2013 |
| IDA Logistics and Transport Ltd | Transport & logistics | 2025 |
| IDA London Holdings Limited | Real estate | 2019 |
| IDA Trans Limited | Transport & logistics | 2017 |
| Idea Taxi Ltd | Information & communication | 2009 |
| Idea Zone Ltd | Construction | 2021 |
| Idea-At Limited | Professional & scientific | 2014 |
| Ideal Cars (Northants) Limited | Wholesale & retail | 2011 |
| Ideal Management Services Limited | Water & waste | 2019 |
| Ideal Property Estates Limited | Real estate | 2022 |
| Ideal Risk Solutions Limited | Financial services | 2019 |
| Idealfx Limited | Financial services | 2004 |
| Idealmastic Ltd | Construction | 2021 |
| Ideas 2 Go Limited | | 2005 |
| Idecorators Ltd | Construction | 2020 |
| Idil Takeway Limited | Hospitality | 2022 |
| IDP Flooring Ltd | Construction | 2016 |
| Idrill + Limited | Professional & scientific | 2009 |
| IDS Electrical Limited | Construction | 1998 |
| Idsc (Decontamination Science) Ltd | Public administration | 2022 |
| IF2020 Limited | Professional & scientific | 2020 |
| Ifda Ltd | Other services | 2025 |
| Ifechi Investment Ltd | Real estate | 2010 |
| IFM Facilities Maintenance Ltd | Construction | 2023 |
| IFN Construction Ltd | Construction | 2015 |
| Ifww Consultants Ltd | Professional & scientific | 2024 |
| IG Mechanical Services Ltd | Construction | 2026 |
| IG UK Construction Ltd | Construction | 2021 |
| Igal Group Ltd | Construction | 2025 |
| Igbo Union Northamptonshire CIC | Other services | 2020 |
| Igdu Engineering Limited | Professional & scientific | 2020 |
| IGE Logistic Limited | Transport & logistics | 2013 |
| IGL Management Limited | Professional & scientific | 2008 |
| Igloo Developments Limited | Real estate | 2017 |
| IGN Estates Ltd | Real estate | 2016 |
| Ignacio Farga Ninoles Limited | Health & social care | 2013 |
| Ignite Commercial Finance Ltd | Financial services | 2024 |
| Igolog Ltd | Administrative & support | 2017 |
| Igor Trans Ltd | Transport & logistics | 2018 |
| Igors Kudrjasovs Ltd | Extraterritorial | 2023 |
| Igpin Ltd | Transport & logistics | 2018 |
| Igreen Hero Limited | Wholesale & retail | 2024 |
| Igroup Technologies UK Limited | Construction | 2013 |
| IGS Projects Limited | Construction | 2014 |
| Igus (UK) Limited | Wholesale & retail | 1991 |
| IH Elite Building Ltd | Construction | 2025 |
| Ihiprojects Ltd | Real estate | 2020 |
| Ihor Transport Ltd | Transport & logistics | 2024 |
| Iidow Online Limited | Wholesale & retail | 2026 |
| Iima Alumni London Limited | Professional & scientific | 2005 |
| Iipj Ltd | Transport & logistics | 2020 |
| IIT Trans Ltd | Administrative & support | 2017 |
| IJ Install Limited | Construction | 2009 |
| IJC Electrical Limited | Administrative & support | 2013 |
| IJF Lighting Ltd | Professional & scientific | 2018 |
| Ijhobbs Consulting Limited | Professional & scientific | 2019 |
| Ijimarv Ltd | Professional & scientific | 2025 |