| ICP Plumbing & Heating Ltd | Construction | 2000 |
| Ictlab Ltd | Information & communication | 2022 |
| Icube Visualization Limited | Information & communication | 2007 |
| ID Suds and Civils Ltd | Professional & scientific | 2025 |
| ID7 Property Ltd | Households | 2025 |
| Idea Cloud Collective Limited | Other services | 2020 |
| Ideal Energy Solutions UK Ltd | Administrative & support | 2017 |
| Ideal Family Cover Ltd | Financial services | 2018 |
| Ideal Flames Limited | Construction | 2019 |
| Ideal Industrial Doors Limited | Construction | 2025 |
| Idealfoodtraders Ltd | Wholesale & retail | 2016 |
| Idealrun Limited | Construction | 2000 |
| Idelo Travel Limited | Administrative & support | 2013 |
| Identity Web Design Limited | Information & communication | 2009 |
| Idioma Limited | Arts & recreation | 2010 |
| IDP Management Limited | Professional & scientific | 2017 |
| Idsworld Ltd | Wholesale & retail | 2020 |
| IEF Research Limited | Professional & scientific | 2008 |
| Iesquared Limited | Administrative & support | 2013 |
| If...Then Limited | Education | 2010 |
| Ifandor Ltd | Professional & scientific | 2009 |
| IFC Trailers Limited | Wholesale & retail | 2016 |
| Iflow Services Ltd | Administrative & support | 2016 |
| IFM Property Limited | Construction | 2022 |
| Ifyke Health Care Ltd | Health & social care | 2022 |
| IG Accounting Ltd | Professional & scientific | 2016 |
| IG Drive Ltd | Transport & logistics | 2021 |
| Igen Capital Ltd | Financial services | 2016 |
| IGIGI2U Limited | Wholesale & retail | 2020 |
| Ignis Heating Ltd | Construction | 2013 |
| Ignis Risk Management Limited | Financial services | 2020 |
| Ignite Finance Limited | Financial services | 2025 |
| Ignite Mechanical and GAS Services Ltd | Construction | 2020 |
| Ignited Ltd | Financial services | 2009 |
| Igreen JK Ltd | Wholesale & retail | 2024 |
| Igunwe Health Care Ltd | Health & social care | 2021 |
| Ijaz & Co Traders Ltd | Construction | 2023 |
| IJB Training Ltd | Education | 2018 |
| Ijem Property Limited | Real estate | 2013 |
| IJP Holdings Limited | Financial services | 2025 |
| Ijyi Ltd | Information & communication | 2014 |
| IKA Academy Ltd | Arts & recreation | 2024 |
| Ikaria Health Limited | Health & social care | 2022 |
| Iknow Mobile Repair Ltd | Manufacturing | 2026 |
| Ikon Training Limited | Other services | 2004 |
| Ikoniko Ltd | Real estate | 2016 |
| Ilford Business Improvement District Limited | Other services | 1997 |
| Illko Ltd | Transport & logistics | 2020 |
| Illuminate Property Development Ltd | Real estate | 2019 |
| Image (Ipswich) Ltd | Other services | 2003 |
| Image Autosales Limited | Wholesale & retail | 2003 |
| Image Ever After Photography Limited | Professional & scientific | 2025 |
| Imes 547 Limited | Other services | 2016 |
| Imfa Global Limited | Information & communication | 2018 |
| IMI 2024 Limited | Transport & logistics | 2024 |
| Imind Your Business Limited | Professional & scientific | 2010 |
| IML Agencies Limited | Transport & logistics | 2002 |
| IML Holdings (Anglia) Limited | Professional & scientific | 2002 |
| Immigration Legal Services (UK) Limited | Professional & scientific | 2011 |
| Imobiliario Limited | Real estate | 2012 |
| Impact & Leadership Holdings Limited | Arts & recreation | 2025 |
| Impact Aggregates Limited | Wholesale & retail | 2011 |
| Impact FX Limited | Arts & recreation | 2013 |
| Impact Sports Tours Ltd | Administrative & support | 2026 |
| Impala Travel Limited | Administrative & support | 2022 |
| Imperial Brickwork Ltd | Construction | 2017 |
| Imperial Crystal Services Limited | Administrative & support | 2025 |
| Imperiale Direct Impact Ltd | Hospitality | 2025 |
| Imperio Food Stores Limited | Hospitality | 2024 |
| Import and Export Keys Ltd | Other services | 2020 |
| Importunity Services Limited | Construction | 2022 |
| Impress Ipswich Limited | Wholesale & retail | 2019 |
| Imprint Consultancy Ltd | Real estate | 2022 |
| Improve Psychological Services Ltd | Health & social care | 2024 |
| IN 2 Beauty Limited | Wholesale & retail | 2017 |
| IN 2 Medical Supplies Ltd | Professional & scientific | 2026 |
| IN Bloom Health Ltd | Health & social care | 2024 |
| IN Path Ltd | Professional & scientific | 2026 |
| IN the English Style Limited | Extraterritorial | 2021 |
| IN Toto Property Services Ltd | Real estate | 2025 |
| IN Your Team Ltd | Information & communication | 2018 |
| Inbervel Limited | Professional & scientific | 2024 |
| Incentive Facilities Management Limited | Administrative & support | 2001 |
| Incentive FM Group Limited | Administrative & support | 2008 |
| Incinerator Replacement Technology Limited | Professional & scientific | 2010 |
| Inclusive Healing Limited | Administrative & support | 2016 |
| Inclusive Opportunities C.I.C. | Health & social care | 2020 |
| Inclusive Studios Ltd | Arts & recreation | 2025 |
| Independent Economics & Finance LLP | | 2012 |
| India Gate Spice Kitchen Ltd | Hospitality | 2026 |
| INDIA444 Ltd | Hospitality | 2019 |
| INDIA50 Ltd | Hospitality | 2023 |
| Indian Bitez Ltd | Hospitality | 2025 |
| Indian Red Spice Ltd | Hospitality | 2024 |
| Indian Spice Massala Ltd | Hospitality | 2023 |
| Indigo Autos Limited | Wholesale & retail | 2007 |
| Indigo Consult Limited | Other services | 2014 |
| Indigo Conveyancing Searches Ltd | Professional & scientific | 2020 |
| Indigo Fields (Lavenham) Management Company Limited | Households | 2020 |
| Indigo Hospitality Ltd | Wholesale & retail | 2022 |