| Ideal Direct Limited | Wholesale & retail | 2001 |
| Ideal Kitchens Kent Ltd | Manufacturing | 2022 |
| Ideal Surveys Limited | Construction | 2010 |
| Ideate Group Limited | Professional & scientific | 2025 |
| Ideploy Ltd | Manufacturing | 2014 |
| IDL Contractors Ltd | Construction | 2017 |
| Idlt Design and Build Ltd | Construction | 2025 |
| Idrissatu Ltd | Health & social care | 2014 |
| Idrizovtrans Limited | Transport & logistics | 2025 |
| Ifacuk CIC | Education | 2025 |
| Ignis Alarms Limited | Construction | 2019 |
| Ignition Support Day Service Ltd | Health & social care | 2024 |
| IH Onuoha Ltd | Construction | 2019 |
| IHK Logistics Ltd | Transport & logistics | 2024 |
| Ihsc Group Ltd | Manufacturing | 2018 |
| Iivii Graphics Ltd. | Professional & scientific | 2016 |
| Iivii Investments Ltd | Hospitality | 2022 |
| IJ Home Groups Ltd | Real estate | 2024 |
| Ikeoluwa Limited | Health & social care | 2022 |
| Ikonic Developments Limited | Construction | 2014 |
| Ikonic Investments Limited | Real estate | 2014 |
| Ilford Staircases Limited | Construction | 2010 |
| IMH Transport and Construction Ltd | Construction | 2024 |
| Imhotep Property Investments Ltd | Real estate | 2019 |
| Immersive Tech Limited | Information & communication | 2025 |
| Impact Plumbing Ltd | Construction | 2023 |
| Impact Professional Solutions Ltd | Information & communication | 2016 |
| Impeccablewins Ltd | Other services | 2024 |
| Imprimis Solutions Limited | Information & communication | 2012 |
| IMS Mail Ltd | Other services | 2015 |
| Imunro Ltd | Wholesale & retail | 2018 |
| Imvk Properties Ltd | Real estate | 2019 |
| Imwcompany Ltd | Wholesale & retail | 2024 |
| Incorporated Rochester Diocesan Board of Education | Education | 1895 |
| Indar Pet Care Ltd | Wholesale & retail | 2025 |
| Independent Care & Support Ltd. | Health & social care | 1999 |
| Indices Limited | Information & communication | 2011 |
| Indiestitch Ltd | Wholesale & retail | 2024 |
| Indigo Collective Ltd | Information & communication | 2024 |
| Indigo UK Holdings Ltd | Financial services | 2021 |
| Industrial Electrical Systems Limited | Construction | 2009 |
| Inerlux Ltd | Wholesale & retail | 2025 |
| Inferno Property Group Ltd | Real estate | 2026 |
| Infinite Globetrotter Ltd | Administrative & support | 2023 |
| Infinity Development Group Limited | Real estate | 2017 |
| Information Technology Support Service Ltd | Information & communication | 2014 |
| Infraco Consulting Limited | Construction | 2023 |
| Infraco Developments Limited | Construction | 2023 |
| Infrastructure Management Limited | Professional & scientific | 2026 |
| Inglemay Limited | Wholesale & retail | 1981 |
| Ingrams Technologies Limited | Professional & scientific | 2015 |
| Initjames Ltd | Administrative & support | 2016 |
| Inkululeko Limited | Administrative & support | 2024 |
| Inline Design Limited | Construction | 1998 |
| Inn Famous Pubs Ltd | Hospitality | 2023 |
| Innchair Solutions Limited | Manufacturing | 2020 |
| Inner Sanctum Therapies Ltd | Other services | 2026 |
| Inniss Properties Limited | Real estate | 2022 |
| Innovation Technology Solutions Global Limited | Wholesale & retail | 2026 |
| INQ Solutions Limited | Information & communication | 2025 |
| Inside Aesthetics Ltd | Other services | 2021 |
| Inside Inclusion Limited | Professional & scientific | 2016 |
| Insight Info-Tech Solutions Limited | Information & communication | 2014 |
| Inspirational Freedom Limited | Information & communication | 2019 |
| Inspire Bespoke Storage Ltd | Other services | 2021 |
| Inspire Telecom Limited | Information & communication | 2019 |
| Instant Fire Protection Ltd | Administrative & support | 2022 |
| Instant Fire Solutions Ltd | Construction | 2025 |
| Institute of Demolition Engineers | Construction | 2012 |
| Institute of Linguists(The) | Education | 1958 |
| Instone Limited | Other services | 2007 |
| Instruction and Design Limited | Information & communication | 2012 |
| Integral Flow Ltd | Water & waste | 2020 |
| Integrity Medicare Ltd | Administrative & support | 2020 |
| Integrity UK Care Solution Ltd | Administrative & support | 2026 |
| Intell Roofing & Building Ltd | Construction | 2024 |
| Intelligent Building Automation Ltd. | Construction | 2005 |
| Intelligent Office Solutions Ltd | Other services | 2007 |
| Interesting Developments Limited | Construction | 2015 |
| Interior 360 Drylining Ltd | Construction | 2026 |
| Interlude Candles Limited | Manufacturing | 2025 |
| Intermedical (UK) Ltd | Wholesale & retail | 1997 |
| Intermedical Limited | Extraterritorial | 2023 |
| Intermedical Supplies Limited | Extraterritorial | 2023 |
| Intermedical UK Holdings Limited | Wholesale & retail | 2023 |
| International Medical Beauty Services and Devices (UK) Limited | Health & social care | 2018 |
| International Nawas Ltd | Construction | 2025 |
| International Study Centre UK Limited | Education | 2018 |
| Intex IT Limited | Information & communication | 2002 |
| Intimate Necessities Ltd | Wholesale & retail | 2025 |
| Intra Arts Ltd | Arts & recreation | 2014 |
| Intra Investments Limited | Real estate | 2024 |
| Intraweb Insight Limited | Information & communication | 2014 |
| Intrinsic Housing Limited | Real estate | 2019 |
| Introland Limited | Construction | 1981 |
| Intruly Ltd | Information & communication | 2016 |
| Invicta Bookkeeping Services Limited | Extraterritorial | 2012 |
| Invicta Fencing Company Limited | Other services | 2007 |
| Invicta Graphics Limited | Manufacturing | 2012 |
| Invicta Installations Ltd | Administrative & support | 2023 |