| Hyka Plumbing & Heating Ltd | Construction | 2020 |
| Hyperion Ophthalmic Limited | Health & social care | 2025 |
| Hypnotized Records UK Ltd | Information & communication | 2021 |
| I & J Scaffolding Group Limited | Financial services | 2022 |
| I & M Garden Services Ltd | Construction | 2018 |
| I H P Foods Ltd | Hospitality | 2019 |
| I R Quince Monumental Mason Limited | Other services | 2005 |
| I.P.M. Personal Pension Trustees Limited | Administrative & support | 1995 |
| I.P.M. Sipp Administration Limited | Financial services | 1994 |
| I.P.M.Sipp Limited | Financial services | 1996 |
| I2I Consultancy Limited | Other services | 2021 |
| I2I Global Holdings Limited | Financial services | 2022 |
| IA Systems Consultancy Limited | Professional & scientific | 2015 |
| Iablonschi Limited | Construction | 2015 |
| Iamc Limited | Professional & scientific | 2018 |
| IAN Battersby Consulting Ltd | Professional & scientific | 2023 |
| IAN Harper Limited | Construction | 2007 |
| Iaspire Systems Limited | Professional & scientific | 2017 |
| IBI Technologies Ltd | Information & communication | 2026 |
| Ibuildup Limited | Construction | 2016 |
| IC4U Limited | Administrative & support | 2013 |
| Iceberg Digital Limited | Information & communication | 2009 |
| Iceberg Ideas Limited | Information & communication | 2009 |
| Iceblock Limited | Real estate | 2013 |
| Ickle Estates Ltd | Real estate | 2023 |
| Icknield Management Limited | Real estate | 1988 |
| Icon in Media Limited | Information & communication | 2009 |
| Iconic Taxi Rentals Limited | Transport & logistics | 2023 |
| Icos Properties Group Limited | Real estate | 2021 |
| ICP Events Limited | Information & communication | 2026 |
| ICS Building Solutions Limited | Construction | 2025 |
| Ictm Services LLP | | 2018 |
| Idax Solutions Ltd | Information & communication | 2013 |
| Idcode Ltd | Information & communication | 2019 |
| Identity Dance Limited | Education | 2018 |
| IDK Nationwide Limited | Other services | 2019 |
| Iemd Limited | Wholesale & retail | 2012 |
| IF Found Group Ltd | Wholesale & retail | 2026 |
| IFA Connect Ltd | Professional & scientific | 2024 |
| IFT Trading Ltd | Information & communication | 2020 |
| IG Plum Ltd | Construction | 2016 |
| Igloos Ltd. | Administrative & support | 1998 |
| Ignite Fire Co Ltd | Administrative & support | 2025 |
| Ignite Fxcorp Ltd | Administrative & support | 2024 |
| Ignite Installations Ltd | Construction | 2011 |
| Ignite My Party Limited | Arts & recreation | 2009 |
| Iiyama (UK) Limited | Information & communication | 1993 |
| IJC Solutions Limited | Information & communication | 2018 |
| Ijoks Ltd | Administrative & support | 2016 |
| Ijoks Property Ltd | Real estate | 2020 |
| Ikigai Group Limited | Hospitality | 2018 |
| Ilginc Exterior Facade Cladding Ltd | Construction | 2020 |
| Ilialuca Limited | Hospitality | 2025 |
| Ilios Partners LLP | | 2022 |
| Illuminaire Capital Limited | Administrative & support | 2020 |
| Illusion Project Management Ltd | Professional & scientific | 2023 |
| Illusion Property Holdings Ltd | Real estate | 2023 |
| IM Products Limited | Extraterritorial | 2018 |
| IMI Construction Limited | Real estate | 2025 |
| IMI Football Academy C.I.C. | Arts & recreation | 2023 |
| IMI Football Academy Development Centre Ltd | Arts & recreation | 2024 |
| IMI Football Academy Sports Ltd | Arts & recreation | 2026 |
| Immersion Ltd | Other services | 2021 |
| Impacct Limited | Administrative & support | 2009 |
| Impact Finance Solutions Limited | Professional & scientific | 2013 |
| Imperium Exports Ltd | Professional & scientific | 2022 |
| Imperium Style Limited | Wholesale & retail | 2018 |
| Impetus Education Ltd | Education | 2022 |
| Impexus Limited | Health & social care | 2011 |
| Implant Solutions London Ltd | Health & social care | 2020 |
| IN and OUT Furniture Ltd | Wholesale & retail | 2024 |
| IN Detail Design Ltd | Other services | 2023 |
| IN Somno Securitas Ltd | Health & social care | 2012 |
| INB Properties Limited | Real estate | 2024 |
| Inboxplacement Ltd | Information & communication | 2018 |
| Inclusive Beauty Limited | Wholesale & retail | 2018 |
| Inclusive Tales Ltd | Manufacturing | 2026 |
| Inclusiveiq Limited | Information & communication | 2025 |
| Incorpai Ltd | Information & communication | 2025 |
| Indalo Pictures Limited | Arts & recreation | 2013 |
| Independent ADR Services Limited | Other services | 2026 |
| Independent Mortgage Advice Bureau (Letchworth) Ltd | Financial services | 2007 |
| Independent Mortgage People Limited | Other services | 2015 |
| India Excel Ltd | Real estate | 2023 |
| Indian Masala Mashup Ltd | Hospitality | 2026 |
| Indian Spice Experience Ltd | Hospitality | 2026 |
| Indigo Services Second Limited | Other services | 2020 |
| Indrain Consulting Limited | Other services | 2018 |
| Industrygeniuses Ltd | Information & communication | 2020 |
| Infanti Properties Limited | Real estate | 2017 |
| Infinite Healthcare Ltd | Health & social care | 2020 |
| Infinity Interiors First Limited | Construction | 2022 |
| Influencer Base Ltd | Information & communication | 2020 |
| Informed Care Limited | Extraterritorial | 2013 |
| Infratek Ltd | Administrative & support | 2021 |
| Ingram Consulting and Coaching Ltd | Professional & scientific | 2022 |
| Inharness Ltd | Professional & scientific | 2014 |
| Injury Recovery Centre Limited | Other services | 2022 |
| Inkredible Cutz Limited | Other services | 2017 |
| Inky Siren Ltd | Arts & recreation | 2025 |