| Innover Solutions Ltd | Real estate | 2019 |
| Innovex Accountants Ltd | Professional & scientific | 2019 |
| Input Digital Ltd | Other services | 2025 |
| Insight Clarity Partnership Limited | Professional & scientific | 2022 |
| Insightfully Ltd | Professional & scientific | 2019 |
| Insite Recruitment Ltd | Other services | 2024 |
| Insitor Ltd | Construction | 2023 |
| Instagrocer Limited | Wholesale & retail | 2024 |
| Instant Properties Ltd | Real estate | 2015 |
| Instant Removals Ltd | Transport & logistics | 2025 |
| Instarooms Ltd | Real estate | 2018 |
| Instinct (Apartments) Management Company Limited | Households | 2010 |
| Inta Electrical Services Ltd | Manufacturing | 2019 |
| Intelligent Information Partners Ltd | Information & communication | 2012 |
| Intelliplus Group Limited | Professional & scientific | 1997 |
| Intelliplus Limited | Information & communication | 1998 |
| Intelliworkspace Ltd | Information & communication | 2010 |
| Intent to Solutions Ltd | Professional & scientific | 2025 |
| Intercall Limited | Administrative & support | 2001 |
| Interest Marketing Limited | Information & communication | 2023 |
| Interfacio Limited | Administrative & support | 2002 |
| Intergrated Security Services Limited | Construction | 2003 |
| Interie Ltd | Wholesale & retail | 2025 |
| Interim Brand Management Solutions Limited | Professional & scientific | 2022 |
| Interlinx Partnership Limited | Administrative & support | 2024 |
| International Evangelism Mission | Other services | 2021 |
| International Justice Development Limited | Administrative & support | 2023 |
| International Pharm-Med Limited | Administrative & support | 2005 |
| International Test Commission Ltd | Professional & scientific | 2020 |
| Internet Telecom Limited | Information & communication | 1999 |
| Internetwork Services (UK) Limited | Information & communication | 1998 |
| Interstellar Property Limited | Real estate | 2025 |
| Interstellar Services Limited | Administrative & support | 2025 |
| Intervalorders Limited | Hospitality | 2008 |
| Intervari Design Limited | Manufacturing | 2021 |
| Introease Ltd | Administrative & support | 2023 |
| Ints Solutions Limited | Information & communication | 2018 |
| INTUU2 Limited | Information & communication | 2023 |
| Invest Reviva Ltd | Hospitality | 2024 |
| Invictus IT Solutions Ltd | Information & communication | 2023 |
| Inxploratus Technologies Ltd | Information & communication | 2021 |
| IOA Group Limited | Information & communication | 2018 |
| Iocosa Limited | Construction | 2002 |
| Ionela Transport Ltd | Transport & logistics | 2025 |
| Iosifi Plumbing Ltd | Construction | 2020 |
| IP Build Ltd | Construction | 2019 |
| IP Media Limited | Financial services | 2008 |
| IP Parking International Ltd | Extraterritorial | 2020 |
| Ipsum Management (UK) Limited | Professional & scientific | 2023 |
| Iqplus Childcare and Educational Services Limited | Education | 2013 |
| IQR Car Sales Ltd | Wholesale & retail | 2024 |
| Irec Multimedia Ltd | Information & communication | 2015 |
| Iris Care Services Ltd | Health & social care | 2020 |
| Iris Electrical Services Limited | Construction | 2015 |
| Irise Personnel Ltd | Administrative & support | 2022 |
| Irmak Sandwich Bar Ltd | Hospitality | 2022 |
| Ironnest Ltd | Administrative & support | 2016 |
| Island to Island Shipping and Removal Limited | Transport & logistics | 2012 |
| Islington Park Mews Residents Limited | Households | 1998 |
| Isobel Asset Management Ltd | Real estate | 2017 |
| Isologix Ltd | Information & communication | 2016 |
| Istanbul Hemel Ltd | Hospitality | 2026 |
| Istanbul Kebab House Ltd | Hospitality | 2023 |
| ISV Freehold Limited | Administrative & support | 2012 |
| IT Stars Recruitment Limited | Administrative & support | 2011 |
| Itab Holdings UK Ltd | Professional & scientific | 2001 |
| Itab Interiors Ltd | Construction | 1973 |
| Itab Shop Products UK Ltd | Wholesale & retail | 2006 |
| Itab UK Ltd | Manufacturing | 1997 |
| Italian Fine Limited | Wholesale & retail | 2020 |
| Itiler Limited | Construction | 2014 |
| Itprodsup Limited | Professional & scientific | 2019 |
| Ivaas & Co Ltd | Wholesale & retail | 2026 |
| Ivel Gardens Resident Management Company Limited | Households | 2021 |
| IVJ Painting & Decorating Ltd | Construction | 2019 |
| Ivory Place (Rifle Hill Braintree) Residents Company Limited | Households | 2009 |
| IW Strength and Conditioning Limited | Arts & recreation | 2025 |
| IWK Holdings Ltd | Construction | 2025 |
| Ixara Ltd | Information & communication | 2012 |
| IY Transway Ltd | Other services | 2013 |
| J & a Security Consulting Limited | Wholesale & retail | 2014 |
| J & V Design Limited | Professional & scientific | 2007 |
| J a GAS & Plumbing Services Limited | Construction | 2002 |
| J Anthony Construction Ltd | Construction | 2017 |
| J Barnes Fencing Ltd | Construction | 2023 |
| J Dunn Civils Ltd | Construction | 2025 |
| J E P Plumbing & Heating Limited | Construction | 2023 |
| J F Bishop & SON Limited | Construction | 2009 |
| J F Day & SON (Builders) Limited | Construction | 1985 |
| J Flack Corporate Travel Ltd | Administrative & support | 2025 |
| J Hollick Limited | Wholesale & retail | 2012 |
| J London Construction Ltd | Construction | 2024 |
| J Mcadam Consulting Ltd | Information & communication | 2018 |
| J Parmenter Construction Ltd | Manufacturing | 2024 |
| J R Glasson Limited | Construction | 2011 |
| J&J Butchers Ltd | Wholesale & retail | 2022 |
| J&J Palmer Groundworks Limited | Construction | 2005 |
| J&M OPS Ltd | Construction | 2024 |
| J&T Online Consulting Ltd | Information & communication | 2022 |
| J. Futcher Limited | Wholesale & retail | 2021 |