| Holdsworth-Vaughan Management Ltd. | Extraterritorial | 2013 |
| Holistic-Flame Ltd | Health & social care | 2018 |
| Holland Park Gate Design & Build Limited | Construction | 2024 |
| Hollywood Square Limited | Information & communication | 2017 |
| Holtby Estates Ltd | Agriculture & fishing | 2025 |
| Home Counties Recruitment Ltd | Administrative & support | 2009 |
| Home Installations Limited | Construction | 1988 |
| Homepride Building Services Ltd | Construction | 1998 |
| Honeysuckle Close MAN Co Ltd | Households | 2022 |
| Hopper Capital Limited | Financial services | 2025 |
| Hopple Limited | Wholesale & retail | 2014 |
| Hopton Street Capital Limited | Professional & scientific | 2024 |
| Horizon Housing Reit PLC | Financial services | 2018 |
| Horizon Infrastructure Partnership Limited | Professional & scientific | 2015 |
| Horizon Investment Holdings (One) Limited | Financial services | 2018 |
| Horizon Investment Holdings (Two) Limited | Financial services | 2018 |
| Horizon Investments (One) Limited | Financial services | 2018 |
| Horizon Investments (Two) Limited | Financial services | 2018 |
| Hosseini Nasab Ltd | Professional & scientific | 2023 |
| Houndbury Management Ltd | Professional & scientific | 2014 |
| House of Wolf Interiors Ltd | Professional & scientific | 2019 |
| Howe Drive Management Company Limited | Households | 2008 |
| Howell Homes Limited | Construction | 2012 |
| Howzat Consulting Limited | Professional & scientific | 2022 |
| HP1T (Aerospace) Limited | Manufacturing | 2018 |
| HP1T (Military and Emergency Services) Limited | Manufacturing | 2018 |
| HP1T (Robotics) Limited | Manufacturing | 2018 |
| HP1T Consulting Limited | Professional & scientific | 2018 |
| HPD (GR) Limited | Real estate | 2015 |
| HPD (Grove Road) Limited | Construction | 2020 |
| HPD Holdings Limited | Financial services | 2019 |
| HPD ST Thomas Bristol Limited | Construction | 2018 |
| HQ Aviation Ltd | Transport & logistics | 2011 |
| HR Digital Media Ltd | Information & communication | 2018 |
| Http Berkshire Limited | Wholesale & retail | 2006 |
| Humlin Group Ltd | Real estate | 2020 |
| Humlin International Holdings Limited | Real estate | 2021 |
| Hurbanot UK Ltd | Wholesale & retail | 2022 |
| Hurst Strategies Ltd | Administrative & support | 2017 |
| Hutton Grove Ltd | Real estate | 2026 |
| Hyde Manor Holdings Limited | Financial services | 2025 |
| Hydravit Ltd | Manufacturing | 2024 |
| Hypx Ltd | Professional & scientific | 2025 |
| Hyscore Limited | Professional & scientific | 2021 |
| Hytec International Limited | Other services | 2020 |
| HZJ Consultancy Limited | Professional & scientific | 2015 |
| I & B Construction Limited | Construction | 2014 |
| I&W Limited | Other services | 2015 |
| IAB Europe (UK) Limited | Professional & scientific | 2018 |
| IAN Cumming Services Limited | Professional & scientific | 2004 |
| Iceberg Power Partners Ltd | Other services | 2019 |
| Icelandic Water Limited | Administrative & support | 2005 |
| Icfo Limited | Administrative & support | 2016 |
| Icona Limited | Professional & scientific | 2022 |
| ICZ Consulting Ltd | Professional & scientific | 2024 |
| Ideal Environments Limited | Administrative & support | 2009 |
| Ideal Pharma Ltd | Health & social care | 2024 |
| Idlewild Consulting Limited | Information & communication | 2017 |
| Ignition Arts Limited | Information & communication | 2013 |
| Igrela Limited | Manufacturing | 2024 |
| IHG Construction Limited | Health & social care | 2021 |
| IHG Healthcare Solutions Limited | Professional & scientific | 2021 |
| IHV GP LLP | | 2026 |
| IHV LP | | 2026 |
| IJK Consultants Limited | Professional & scientific | 2016 |
| Imari Entertainment Limited | Information & communication | 1999 |
| Immersive Depths Ltd | Wholesale & retail | 2024 |
| Imnaii Global Business (IGB) Ltd | Wholesale & retail | 2016 |
| Impact Medical Education Limited | Professional & scientific | 2014 |
| Impacted Consulting Limited | Information & communication | 2023 |
| Impacted Group Limited | Financial services | 2022 |
| Impacted Group Trustees Limited | Professional & scientific | 2025 |
| Impacted Limited | Information & communication | 2022 |
| Impacted SIV Limited | Information & communication | 2017 |
| Impacted TWP Limited | Professional & scientific | 2025 |
| Imperial One Limited | Other services | 2008 |
| Importantly Ltd | Administrative & support | 2014 |
| Improvit Consulting Ltd | Information & communication | 2010 |
| Inbeeo Ltd | Professional & scientific | 2016 |
| Independent Marketing Sciences Limited | Professional & scientific | 2005 |
| Indotronix Avani UK, Ltd. | Information & communication | 2022 |
| Industrial & Export Consultancy Services Limited | Construction | 1965 |
| Industrial Total Diesel Ltd | Wholesale & retail | 2018 |
| Infinite Holdings & Investments Ltd | Financial services | 2024 |
| Infinitude Limited | Information & communication | 2016 |
| Infinity IO Ltd | Information & communication | 2024 |
| Infobuffalo Ltd | Information & communication | 2025 |
| Infotrend Limited | Information & communication | 1988 |
| Infrastructure Partnership LLP | | 2013 |
| Infraviolet Limited | Information & communication | 2009 |
| Ingletone Limited | Information & communication | 2014 |
| Inhealth Audiology and ENT Limited | Health & social care | 2023 |
| Inhealth Cardiology Limited | Health & social care | 2025 |
| Inhealth Cats Limited | Health & social care | 2017 |
| Inhealth Diagnostic & Imaging Limited | Professional & scientific | 2002 |
| Inhealth Echotech Limited | Health & social care | 2001 |
| Inhealth Endoscopy Limited | Health & social care | 2008 |
| Inhealth Facilities Management Limited | Administrative & support | 1997 |
| Inhealth Group Holdings PLC | Professional & scientific | 2005 |
| Inhealth Group Limited | Professional & scientific | 2002 |