| Horne & Co Ltd | Financial services | 2020 |
| Hostudio Ltd. | Information & communication | 2012 |
| Hounslow Tyres Limited | Administrative & support | 2000 |
| House of Blenner Ltd | Professional & scientific | 2013 |
| House of VK Limited | Wholesale & retail | 2026 |
| House Proud Contractors Ltd | Real estate | 2017 |
| Howard Court RTM Company Limited | Households | 2021 |
| HPM Plumbing & Heating Ltd | Construction | 2020 |
| HPO Hospitality Ltd | Hospitality | 2025 |
| HR & Books Co. Ltd | Administrative & support | 2023 |
| HR Samra Homes Ltd | Real estate | 2026 |
| HSD Building & Construction Ltd | Construction | 2025 |
| HT Tech Ltd | Information & communication | 2026 |
| Human Guided Learning Limited | Education | 2024 |
| Hunter Plumbing Ltd | Construction | 2022 |
| Huper Solutions Limited | Professional & scientific | 2010 |
| Hursell Building Projects Ltd | Construction | 2021 |
| Hurst Primary School | Education | 2013 |
| Hush Little Short Ltd | Information & communication | 2025 |
| HV Property Solutions Ltd | Real estate | 2022 |
| HWM Property Ltd | Real estate | 2016 |
| Hwyke Consultants Ltd | Professional & scientific | 2014 |
| Hyde Music Ltd | Arts & recreation | 2013 |
| Hyperledger Ltd | Information & communication | 2025 |
| Hypescaling Ltd | Wholesale & retail | 2026 |
| Hytech Designs Limited | Real estate | 2000 |
| I Craft Limited | Construction | 2025 |
| I Panta Ltd | Construction | 2017 |
| I. O . Electricals Limited | Manufacturing | 2017 |
| I.D Windows Cleaning Services Ltd | Administrative & support | 2025 |
| I.K Removals Services Ltd | Transport & logistics | 2023 |
| I.S.S Investment Limited | Financial services | 2024 |
| IB Microscopes Limited | Manufacturing | 2012 |
| IC Media SE Ltd | Arts & recreation | 2023 |
| ICT (London) Limited | Administrative & support | 1980 |
| Idemitsu Europe Ltd. | Financial services | 2026 |
| Ignet Limited | Education | 2014 |
| Ignite Plumbing Heating and GAS Ltd | Construction | 2019 |
| IGT Limited | Administrative & support | 2026 |
| IHE Consultancy Limited | Financial services | 2018 |
| Ileco Ltd | Real estate | 2022 |
| Illusion Entertainment Ltd | Information & communication | 2026 |
| Imedy Limited | Health & social care | 2013 |
| Imperative Doing Limited | Extraterritorial | 2007 |
| Imperative Insight Limited | Extraterritorial | 2007 |
| In-House Partners Limited | Administrative & support | 2019 |
| Infallible Limited | Professional & scientific | 2005 |
| Infrastructure Capital Development Finance Limited | Financial services | 2023 |
| Inglewood Court (Bromley) Management Limited | Households | 1986 |
| Inglewood Court (Bromley) RTM Company Limited | Real estate | 2021 |
| Inglourious Mailers LLP | | 2024 |
| Ingress Training Limited | Education | 2021 |
| Inkwa Tattoos Ltd | Arts & recreation | 2012 |
| Inner City Drainage Solutions Ltd | Other services | 2019 |
| Innovation Bay Ltd | Information & communication | 2021 |
| Innovo Apartments Management Company Limited | Households | 2020 |
| Inspire Design & Management Limited | Wholesale & retail | 2019 |
| Instrument Research Company Limited | Manufacturing | 2014 |
| Integrated Performance Ltd | Health & social care | 2026 |
| Intelligent Fire Solutions Ltd | Administrative & support | 2019 |
| IO Estates Ltd | Real estate | 2023 |
| IPD Project Services Limited | Professional & scientific | 2025 |
| Ipek Edipoglu Ltd | Health & social care | 2025 |
| IQ Project Management Limited | Professional & scientific | 2025 |
| Isco Ventures and Property Management Limited | Real estate | 2019 |
| ISV Deli Ltd | Hospitality | 2024 |
| ITS a Hard Life Limited | Financial services | 2021 |
| IYE Production House Limited | Health & social care | 2020 |
| J & B Green Energy Ltd | Energy | 2012 |
| J & E Property Services Limited | Construction | 2013 |
| J & W Hards Limited | Construction | 2015 |
| J a Slates Ltd | Wholesale & retail | 2015 |
| J Bemrose T/A J & K Transport (UK) Ltd | Extraterritorial | 2013 |
| J C Electrical Limited | Construction | 2003 |
| J Cohen Limited | Health & social care | 2015 |
| J D Jackmenn Ltd | Professional & scientific | 2016 |
| J Deacon Consultants Ltd | Professional & scientific | 2025 |
| J E L Heating & Plumbing Ltd | Construction | 2017 |
| J G C Engineering Limited | Energy | 2017 |
| J Greenaway Holdings Limited | Arts & recreation | 2025 |
| J M W Vicary Limited | Wholesale & retail | 2002 |
| J Webb Ltd | Construction | 2025 |
| J&E Lifts Ltd | Construction | 2021 |
| J&R Drainage Services Ltd | Water & waste | 2025 |
| J. B. GAS Services Limited | Construction | 2008 |
| J. P. O`Keeffe Plumbing & Heating Limited | Construction | 2007 |
| J.B Social Work Limited | Health & social care | 2014 |
| J.D.Painters Ltd | Construction | 2018 |
| J.E.H Plumbing Services Ltd | Construction | 2021 |
| J.G.R. Interiors Limited | Construction | 2006 |
| J.Grant Services Ltd | Professional & scientific | 2025 |
| J.M. Scarff Limited | Manufacturing | 2002 |
| J.M.K. Care Services Limited | Other services | 2007 |
| Jabc Limited | Wholesale & retail | 2013 |
| Jacey 2017 Limited | Construction | 2017 |
| Jacko Ltd | Information & communication | 2011 |
| Jacoah Consulting Limited | Professional & scientific | 2019 |
| Jadt Limited | Wholesale & retail | 2013 |
| Jaevy Limited | Real estate | 2024 |
| JAG Capital Partners (UK) Limited | Financial services | 2023 |