| Head of House Designs Limited | Professional & scientific | 2014 |
| Head of House Properties Limited | Real estate | 2021 |
| Heartspace Yoga Ltd | Arts & recreation | 2024 |
| Heathshott Property Management Limited | Households | 1991 |
| Hebros Abseiling Services Ltd | Construction | 2016 |
| Heid & Seek Social Ltd | Professional & scientific | 2024 |
| Helene Cross Consulting Limited | Professional & scientific | 2025 |
| Henkind Ltd | Manufacturing | 2026 |
| Henley Shipping Limited | Administrative & support | 2016 |
| Hennessy Cleaning Contractors Ltd | Administrative & support | 2004 |
| Henrut Transportation Ltd | Transport & logistics | 2015 |
| Henshaw Bentley Limited | Professional & scientific | 2021 |
| Hexanode Technologies Limited | Information & communication | 2018 |
| Hilltop Business Consulting Limited | Professional & scientific | 2026 |
| Hilo Management Limited | Real estate | 2001 |
| Hilton Mountford Limited | Professional & scientific | 2024 |
| Hitchcock Architects Ltd | Construction | 2015 |
| HMS Financial Services Limited | Financial services | 2019 |
| Holistic Lifepath Limited | Professional & scientific | 2015 |
| Hollis Projects Ltd | Administrative & support | 2025 |
| Holly House Property Management Company Limited | Households | 1988 |
| Home From Home Living Ltd | Hospitality | 2013 |
| Home Matters Financial Services Ltd | Real estate | 2022 |
| Honey Tilley Limited | Wholesale & retail | 1996 |
| Hooper Court Residents Company Limited | Households | 2007 |
| Houlihan & Co (Group) Limited | Financial services | 2024 |
| Houlihan & Co (Holdings) Limited | Financial services | 2014 |
| Houlihan & Co. (Excavations) Limited | Construction | 1972 |
| Houlihan and Co Limited | Administrative & support | 2002 |
| House of Asia Ltd | Wholesale & retail | 2018 |
| Howards Court Residents Company Limited | Households | 2009 |
| HPR Building Solutions Limited | Real estate | 2025 |
| HRH Sports Consultancy Limited | Arts & recreation | 2017 |
| HSV Tech Limited | Information & communication | 2023 |
| HT Company (Essex) Ltd | Real estate | 2010 |
| Huckleberry Sport Limited | Administrative & support | 2017 |
| Hucks Boatyard Ltd | Manufacturing | 2025 |
| HUH Trading Limited | Wholesale & retail | 2026 |
| Hustle and Leverage Consulting Ltd | Administrative & support | 2026 |
| Hyde Park Realty Limited | Real estate | 2020 |
| Hydtec Ltd | Financial services | 2024 |
| I S Solutions Ltd | Information & communication | 2011 |
| I-Nocarbon Limited | Information & communication | 2020 |
| Ice First AID Training Limited | Education | 2012 |
| ICY N Spicy Sunbury Limited | Hospitality | 2025 |
| Ideodes Consulting Ltd | Professional & scientific | 2021 |
| IGA Investments Ltd | Real estate | 2024 |
| Ignite Fitness Ltd | Arts & recreation | 2021 |
| Ignite Fitness Online Coaching Ltd | Other services | 2025 |
| IJM Richmond Limited | Professional & scientific | 2011 |
| Illuminat FX Ltd | Education | 2019 |
| Image Business Limited | Administrative & support | 2000 |
| Imaginic Solution Ltd | Administrative & support | 2022 |
| Imanas London Limited | Health & social care | 2015 |
| Impacto Creative Ltd | Information & communication | 2025 |
| Imperialat Limited | Administrative & support | 2017 |
| Imranamiri Ltd | Wholesale & retail | 2025 |
| Incito Consultants Limited | Information & communication | 2012 |
| Indalo Electric Ltd | Construction | 2024 |
| Independent Grip Limited | Administrative & support | 2007 |
| Infinity Nexus Tech Ltd | Information & communication | 2024 |
| Influence Power Magazine Limited | Manufacturing | 2025 |
| Info Trading Ltd | Financial services | 2020 |
| Infotech Valley Ltd | Information & communication | 2012 |
| Innovare Globe Tech Limited | Information & communication | 2024 |
| Inside Track Marketing Ltd | Professional & scientific | 2025 |
| Inspirational Management Services Ltd | Professional & scientific | 2006 |
| Instanter Learning Trust | Education | 2012 |
| Intelogy Limited | Information & communication | 1995 |
| International Assessment Bureau Ltd | Professional & scientific | 2024 |
| International Aviation Ltd | Administrative & support | 2023 |
| Intertek Fire Solutions Ltd | Administrative & support | 2022 |
| Intraciti Ltd | Administrative & support | 2014 |
| Intueri Advisors Ltd | Administrative & support | 2026 |
| Invitology Limited | Information & communication | 2021 |
| IP Home Solutions Ltd | Construction | 2026 |
| Ircc Ltd | Professional & scientific | 2025 |
| Iris Security Solutions Ltd | Administrative & support | 2015 |
| Irvsax Music Ltd | Administrative & support | 2012 |
| Ismile Dental Limited | Health & social care | 2019 |
| IVY Mansion (Interests) Limited | Real estate | 1981 |
| J & J Construction Services Ltd | Construction | 1999 |
| J D Campbell Creative Ltd | Administrative & support | 2024 |
| J S Jewels Limited | Other services | 2009 |
| J&Kh Services Ltd | Transport & logistics | 2017 |
| J.S.A.H Ltd | Manufacturing | 2015 |
| Ja&B Ltd | Transport & logistics | 2019 |
| Jacqueline's Garden Community Interest Company | Water & waste | 2020 |
| Jacques NEL Limited | Information & communication | 2019 |
| Jaggi Garderner Ltd | Construction | 2021 |
| Jaja Ltd | Construction | 2025 |
| Jamb Associates Limited | Information & communication | 2016 |
| Janus Arts Limited | Arts & recreation | 2018 |
| Janus Jewels Limited | Arts & recreation | 2018 |
| JB E-Propulsion Technologies Ltd | Professional & scientific | 2024 |
| JBC Property Holdings Ltd | Real estate | 2022 |
| JBC Sports Limited | Wholesale & retail | 2021 |
| Jc's Quality Consulting Ltd | Construction | 2010 |
| JCI Emea Holdings Limited | Financial services | 2019 |
| JCI European Holdings Limited | Financial services | 2020 |