| Hfce UK Ltd | Professional & scientific | 2021 |
| HHH Haven Aura Ltd | Wholesale & retail | 2026 |
| Hi-Tech Investments Limited | Construction | 1999 |
| Hicq Ltd. | Wholesale & retail | 2016 |
| High END Recruitment Agency Limited | Administrative & support | 2021 |
| High Standard Communications Limited | Information & communication | 2021 |
| Highest Mountain Ltd | Health & social care | 2011 |
| Highfield Drive Management Ltd | Real estate | 2025 |
| Highways & Konnection Services Ltd | Construction | 2019 |
| Hilal Capital UK Limited | Professional & scientific | 2024 |
| Hilal Consulting UK Limited | Professional & scientific | 2024 |
| Hill Drive Autos Limited | Wholesale & retail | 2024 |
| Hillcrest Harlow Management Company Limited | Households | 2025 |
| Hinckley Ltd | Real estate | 2026 |
| HJ Designbuild Ltd | Construction | 2019 |
| HK26 Ltd | Real estate | 2020 |
| HLN Accounts Limited | Professional & scientific | 2022 |
| HM3 Health Ltd | Health & social care | 2019 |
| HMC International Ltd | Information & communication | 2025 |
| HMS Trades Ltd | Wholesale & retail | 2023 |
| Hoal MED Ltd | Health & social care | 2026 |
| Hoffman Communications Ltd | Professional & scientific | 2021 |
| Holistic Adhd Limited | Health & social care | 2021 |
| Holland House TW7 Limited | Construction | 2018 |
| Holly Bryan Associates Limited | Professional & scientific | 2016 |
| Holly IP Limited | Professional & scientific | 2011 |
| Holmefield Court Property Management Company Limited | Households | 1965 |
| Holo Commerce Ltd | Information & communication | 2025 |
| Honey Badger Grips Ltd | Information & communication | 2012 |
| Honores Patisserie Limited | Manufacturing | 2020 |
| Horizon Educational Psychology Ltd | Education | 2023 |
| Hotel Caminito Ltd | Administrative & support | 2010 |
| Hotel Nights Limited | Administrative & support | 2013 |
| Hounslow BID Ltd | Administrative & support | 2025 |
| Hounslow Symphony Orchestra Productions Ltd | Arts & recreation | 2018 |
| Hounslow’S Heart BID Ltd | Administrative & support | 2025 |
| House of Publicans Ltd | Hospitality | 2016 |
| Hovafly Limited | Professional & scientific | 2021 |
| HR People & Strategic Solutions Limited | Professional & scientific | 2025 |
| HRK Solutions Ltd | Transport & logistics | 2016 |
| HS Mart Limited | Wholesale & retail | 2025 |
| HSA & RKA Properties Ltd | Real estate | 2019 |
| HTT Trades Ltd | Wholesale & retail | 2023 |
| Huho Ltd | Wholesale & retail | 2025 |
| Hujra Limited | Wholesale & retail | 2021 |
| Hulin Associates Limited | Construction | 2011 |
| Human-Driven AI CIC | Education | 2025 |
| Humble HUT Ltd | Real estate | 2024 |
| Hunger HUT Ltd | Hospitality | 2025 |
| Hunter Doors and Windows Limited | Manufacturing | 2025 |
| Hunton Leonardo Limited | Education | 2025 |
| Hynesite London Limited | Construction | 2022 |
| Hyperian Homes Ltd | Real estate | 2024 |
| Hypernextech Limited | Information & communication | 2024 |
| Hysteric Flora Limited | Information & communication | 2017 |
| HZA Investment Limited | Real estate | 2025 |
| HZN Associates Limited | Health & social care | 2018 |
| I AM Aether Ltd | Other services | 2019 |
| I Love Plumbing Limited | Construction | 2011 |
| I Move (London) Limited | Administrative & support | 2009 |
| I&S Design Studios Ltd | Real estate | 2024 |
| I.A.J.D. Limited | Administrative & support | 2019 |
| Iboomi Limited | Real estate | 2015 |
| Ichigo Ichie Travel Ltd | Administrative & support | 2003 |
| Iconic Building Services Limited | Construction | 2025 |
| Iconic NOW Limited | Professional & scientific | 2022 |
| Ideal Clean Ltd | Administrative & support | 2025 |
| Identity OS Ltd | Information & communication | 2026 |
| Idese Interior Designs Ltd | Professional & scientific | 2012 |
| IDL Trading Ltd | Professional & scientific | 2021 |
| IDM Investments Limited | Real estate | 2020 |
| Idyllica Ltd | Wholesale & retail | 2020 |
| Igenie Limited | Information & communication | 2010 |
| IGK Limited | Administrative & support | 2003 |
| Ignis Overseas Ltd | Wholesale & retail | 2021 |
| Igrey Post Ltd | Information & communication | 2025 |
| IHS Charis International Ltd | Hospitality | 2025 |
| Illuminate Strategy Consulting Limited | Administrative & support | 2025 |
| ILM Consulting Limited | Wholesale & retail | 2025 |
| Ilmi Tech Ltd | Wholesale & retail | 2025 |
| IM Estates Limited | Financial services | 2013 |
| Imagewear Limited | Wholesale & retail | 1973 |
| Imbrex Roofing Ltd | Construction | 2020 |
| Imedia Distribution Limited | Wholesale & retail | 2009 |
| Imedia Smart Home Integration Ltd | Information & communication | 2021 |
| Imko Ltd | Construction | 2010 |
| Imko Premier Limited | Construction | 2019 |
| Imosi Limited | Real estate | 2018 |
| IMP Consultants Ltd | Administrative & support | 2019 |
| Impact Dance Foundation C.I.C. | Education | 2019 |
| Impact Dance Limited | Arts & recreation | 2017 |
| Impelto Ltd | Real estate | 2024 |
| Imperial Empire Building Limited | Construction | 2022 |
| Imperial Telecom Limited | Information & communication | 2013 |
| IN Market Access Ltd | Professional & scientific | 2009 |
| IN Opera (UK) Limited | Manufacturing | 2009 |
| IN Opera Contracts Ltd. | Manufacturing | 2003 |
| IN Zaire Ltd | Extraterritorial | 2019 |
| Inacoe Media Ltd | Information & communication | 2024 |
| Incedo Biotech Enterprises Limited | Extraterritorial | 2017 |