| Headstart Day and Afterschool Care Limited | Education | 2002 |
| Headwood Limited | Households | 2024 |
| Healthcare Focus Ltd | Administrative & support | 2019 |
| Heart of Home Designs Limited | Manufacturing | 2020 |
| Hearth and Hall Living History Centre Ltd | Arts & recreation | 2025 |
| Heatweb Solutions Limited | Construction | 2023 |
| Heddon Holdings Limited | Financial services | 1995 |
| Hedges Chandler (Sudbury) Limited | Professional & scientific | 1999 |
| Hedges Chandler (Westcliff) Limited | Professional & scientific | 1998 |
| Heifix Ltd | Wholesale & retail | 2024 |
| Helen Harding Ltd | Professional & scientific | 2013 |
| Helen House Management Association Limited | Households | 1993 |
| Helmsman Services Limited | Administrative & support | 2000 |
| Hemps Green Equestrian Ltd | Education | 2014 |
| Hennessy's Fits Ltd | Wholesale & retail | 2025 |
| Henny Show Supplies Ltd | Manufacturing | 2018 |
| Herbert & Justice Limited | Construction | 2018 |
| Heritage Roadways Limited | Construction | 2025 |
| Heritage Service Group Ltd. | Real estate | 1999 |
| Heritage Thread Ltd | Other services | 2024 |
| Heritage U.K. Ltd | Construction | 2018 |
| Hermitage Conservation Limited | Other services | 2026 |
| Herringswell Mews Management Limited | Households | 2020 |
| Hetty Feather Pictures Limited | Information & communication | 2017 |
| Hevaura Ltd | Manufacturing | 2026 |
| HG Passive Fire Ltd | Construction | 2023 |
| High House Furniture Ltd | Manufacturing | 2015 |
| High Quality Installations Limited | Construction | 2024 |
| Hill Farm Joinery Ltd | Construction | 2015 |
| Hinesight Ltd | Professional & scientific | 2024 |
| Historical Games Community Interest Company | Administrative & support | 2023 |
| HMT Machine Hire Limited | Administrative & support | 2011 |
| HMT Machinery Ltd | Administrative & support | 2004 |
| Holdam Limited | Other services | 2010 |
| Holiday With Style Ltd | Hospitality | 2023 |
| Holly Bullock Studios Limited | Other services | 2025 |
| Holmes Decorating Limited | Construction | 2019 |
| Homes Plus Care Limited | Health & social care | 2009 |
| Honestly Unofficial Ltd | Wholesale & retail | 2020 |
| Hoopers a M Limited | Other services | 2024 |
| Horizon Capital Investment Limited | Financial services | 2017 |
| Horizon Park Holdings Ltd | Construction | 2026 |
| Horizon Phone Shop UK Ltd | Wholesale & retail | 2024 |
| Horndon Place Management Co Limited | Households | 2019 |
| Hornets Tech Limited | Information & communication | 2006 |
| Hornsey's Boutique Limited | Wholesale & retail | 2025 |
| Hospital MAP App Limited | Information & communication | 2015 |
| Houghton Bloodstock UK Limited | Agriculture & fishing | 2005 |
| Houghton Hall Farm Limited | Extraterritorial | 1939 |
| Houghton Homes (Ipswich) Ltd | Real estate | 2018 |
| Hourglass (Safer Ageing) | Information & communication | 2010 |
| Howlett of Lavenham Limited | Wholesale & retail | 1998 |
| HPL Commercial Properties Limited | Real estate | 2024 |
| Hsil Corp Limited | Professional & scientific | 2026 |
| Hub @ the Hart Limited | Hospitality | 2024 |
| Huckle Building & Contractors Ltd | Construction | 2020 |
| Huizen UK Limited | Real estate | 2024 |
| Humble Beginnings Campervans Limited | Wholesale & retail | 2025 |
| Hushwing Ltd | Professional & scientific | 2023 |
| Hutchins Creative Limited | Professional & scientific | 2011 |
| I AM Nobilis Ltd | Other services | 2009 |
| I D S Leasing Limited | Real estate | 1992 |
| I.D.S. U.K. Limited | Extraterritorial | 2008 |
| I.W Kiddy Plant Hire Ltd. | Administrative & support | 2011 |
| IAN Mcgraw Ltd | Transport & logistics | 2013 |
| IC Offshore Services Limited | Professional & scientific | 2012 |
| Iceni Digital Consulting Ltd | Information & communication | 2025 |
| Ickworth Trade Finance Ltd | Professional & scientific | 2016 |
| Iconfair Limited | Professional & scientific | 1974 |
| Iconic Interactive Ltd. | Information & communication | 2023 |
| ICS Telecoms Limited | Administrative & support | 2016 |
| Idea Printers Limited | Professional & scientific | 2026 |
| Ideasbarn Ltd | Information & communication | 2019 |
| Iflscience Limited | Information & communication | 2015 |
| IKB Capital Limited | Financial services | 2001 |
| Ikigai Legal Ltd | Professional & scientific | 2022 |
| IMC Elite Properties Ltd | Real estate | 2024 |
| Imhof Trading Limited | Administrative & support | 2012 |
| Impact Business Services Ltd | Professional & scientific | 2026 |
| Impact Lawyers Ltd | Professional & scientific | 2024 |
| Impact Tech Ltd | Information & communication | 2025 |
| Impala Stone Limited | Manufacturing | 2006 |
| Imperial Heights (Bracknell) Management Limited | Households | 2007 |
| Impervious Flat Roofing Ltd | Construction | 2021 |
| IN for a Penney Limited | Professional & scientific | 2023 |
| IN Product Ltd | Administrative & support | 2022 |
| Inc JEN Media Ltd | Manufacturing | 2012 |
| Incipere Limited | Professional & scientific | 2014 |
| Independent Surveying Consultants Ltd | Professional & scientific | 2020 |
| Indexal Limited | Hospitality | 2015 |
| Indivio Care Ltd | Health & social care | 2025 |
| Induspec Ltd | Other services | 2008 |
| Infinitest Limited | Information & communication | 2025 |
| INNOV8IVE Property Group Limited | Real estate | 2026 |
| Insight AP Ltd | Education | 2026 |
| Insight Film Productions Ltd | Information & communication | 2024 |
| Insight TWI Films Ltd | Information & communication | 2021 |
| Instructorbox Limited | Information & communication | 2016 |
| Interior Day Limited | Administrative & support | 2023 |
| Interior Night Limited | Administrative & support | 2016 |