| Hamilton Refurbishments Ltd | Construction | 2012 |
| Happy Space Design LLP | | 2019 |
| Hardwick Property Holdings Ltd | Real estate | 2021 |
| Hardwick Property Solutions Ltd | Real estate | 2021 |
| Harmony CF Limited | Real estate | 2018 |
| Harmony JF Limited | Real estate | 2017 |
| Hawkers Hill Energy Park Limited | Construction | 2016 |
| Hawn Holdings Ltd | Professional & scientific | 2026 |
| Hazel Renewables Limited | Energy | 2012 |
| Hazelhurst Ventures Ltd | Construction | 2020 |
| HBS 001 Ltd | Extraterritorial | 2007 |
| HBS 049 Ltd | Administrative & support | 2007 |
| Hcreative Marketing Limited | Professional & scientific | 2024 |
| Head Down Scenic Ltd | Manufacturing | 2025 |
| Health Journey Heroes Limited | Information & communication | 2026 |
| Health Snobs Ltd | Wholesale & retail | 2026 |
| Heart Reef Ltd | Financial services | 2025 |
| Heartsmap Limited | Other services | 2014 |
| Heathstead Limited | Water & waste | 2026 |
| Heliosphan Ltd | Arts & recreation | 2025 |
| Hepburn Sons Limited | Professional & scientific | 1989 |
| Heron Property Lettings Ltd | Real estate | 2018 |
| Herts Double Glazing and Pergolas Limited | Construction | 2014 |
| Herts NLP Ltd | Education | 2021 |
| Hexcad Ltd | Professional & scientific | 2019 |
| HH Global Goods Limited | Wholesale & retail | 2025 |
| High Down Limited | Energy | 2010 |
| High Haswell Limited | Energy | 2011 |
| High POW Windfarm Limited | Energy | 2011 |
| High Sharpley Limited | Energy | 2011 |
| High Spec Car Sales and Detailing Ltd | Wholesale & retail | 2022 |
| Hill Farm (Phase Three) Management Company Limited | Administrative & support | 2011 |
| Hill Farm (the Barns) Management Company Limited | Real estate | 2009 |
| Hill of Fare Energy Limited | Energy | 2024 |
| Hill of Towie Limited | Administrative & support | 2009 |
| Hilltop 2016 Ltd | Wholesale & retail | 2016 |
| HMG Marks Limited | Professional & scientific | 2018 |
| HN Electrical Solutions Limited | Construction | 2016 |
| Hopon Mobility (UK) Limited | Financial services | 2021 |
| Horizon Payroll Solutions Limited | Extraterritorial | 2021 |
| Horizon RCS Europe Limited | Extraterritorial | 2007 |
| Horohoe Construction Limited | Construction | 1998 |
| Horohoe Properties Ltd | Real estate | 2007 |
| Hrid Atelier Ltd | Professional & scientific | 2025 |
| Huddersfield Estates and Land Ltd | Real estate | 2026 |
| Humpdays Ltd | Information & communication | 2024 |
| Hunting Verney Limited | Real estate | 2010 |
| Huntley Hobbies Ltd | Wholesale & retail | 2013 |
| Hunton Trading Limited | Hospitality | 2021 |
| HW Assure Group Limited | Administrative & support | 2026 |
| I-Automate Ltd | Construction | 2011 |
| IBM Estates Ltd | Real estate | 2022 |
| Ideas 2 Launch Limited | Professional & scientific | 2012 |
| IHA Associates Ltd | Professional & scientific | 2023 |
| Image Supply Ltd | Extraterritorial | 2007 |
| Imagination Technologies Group Limited | Information & communication | 1994 |
| Imagination Technologies Limited | Information & communication | 1977 |
| Imdg Invesco Ltd | Real estate | 2019 |
| Immico Ltd | Manufacturing | 2019 |
| Imperfectly Natural Limited | Information & communication | 2006 |
| IN2GR8MENTALHEALTH C.I.C. | Health & social care | 2021 |
| Indigozest Limited | Information & communication | 2010 |
| Indradhanushkids Academy Community Interest Company | Arts & recreation | 2023 |
| Industrial Scrap Processing Limited | Professional & scientific | 1984 |
| Inflow Media Limited | Information & communication | 2023 |
| Informedconsent Ltd | Information & communication | 2018 |
| Innagreen GP Co Limited | Financial services | 2021 |
| Innagreen Investments LLP | | 2021 |
| Innagreen Limited | Financial services | 2021 |
| Innagreen Management Limited | Financial services | 2021 |
| Innagreen One Limited | Financial services | 2022 |
| Innagreen Projects Limited | Financial services | 2025 |
| Inspire Land and Planning Ltd | Real estate | 2020 |
| Inspiring Steps C.I.C. | Education | 2015 |
| Intelligent Concepts Ltd | Professional & scientific | 2020 |
| International Wheels Ltd | Wholesale & retail | 2019 |
| Intouch Planning and Development Limited | Professional & scientific | 2019 |
| Intouch Planning Limited | Professional & scientific | 2017 |
| Investorhub Ltd | Information & communication | 2023 |
| Iqlink Ltd | Information & communication | 2004 |
| Islington Partners Ltd | Information & communication | 2013 |
| Itech Computers Services Ltd | Information & communication | 2017 |
| J & L Commerce Limited | Wholesale & retail | 2020 |
| J L F Race Events Ltd | Arts & recreation | 2010 |
| J&Ck Ltd | Administrative & support | 2017 |
| J&CK9 Ltd | Other services | 2026 |
| J&M Property Holdings Limited | Real estate | 2017 |
| J&O London Ltd | Wholesale & retail | 2024 |
| J. K. Rail Limited | Construction | 2006 |
| J.Caro Ltd | Financial services | 2024 |
| J.Field Builders Limited | Construction | 2019 |
| Jack in the Box at Brockswood CIC | Education | 2019 |
| Jack in the Box Nursery Limited | Education | 2016 |
| Jack of ALL AI Limited | Information & communication | 2023 |
| Jacobs and Vale Limited | Wholesale & retail | 2024 |
| Jade Hutchings Ltd | Arts & recreation | 2026 |
| Jaimelerima Ltd | Real estate | 2022 |
| Jamella Estates Ltd | Real estate | 2019 |
| Jamie WEY Limited | Extraterritorial | 2005 |
| Jamtom Limited | Real estate | 2019 |