| Hutchings & Harding Limited | Manufacturing | 1922 |
| Hutton Property Limited | Real estate | 2012 |
| Hutuleac Logistics Ltd | Transport & logistics | 2017 |
| Huxleys Car Hire Ltd | Transport & logistics | 2018 |
| Huxton & KAM Limited | Administrative & support | 2025 |
| Huzzl Limited | Construction | 2020 |
| HV Locum Services Ltd | Health & social care | 2022 |
| HV Property Holding Ltd | Real estate | 2021 |
| Hvac Sales Ltd | Extraterritorial | 2022 |
| Hvekaria Ltd | Professional & scientific | 2023 |
| HVG Trading Ltd | Professional & scientific | 2016 |
| HVK Productions UK Limited | Arts & recreation | 2023 |
| HWH Energy Limited | Water & waste | 2013 |
| HY Construction Ltd | Construction | 2025 |
| HY Industry Ltd | Education | 2025 |
| HYB Optics Ltd | Wholesale & retail | 2025 |
| Hybrid Glazings Ltd | Construction | 2024 |
| Hybrid Property Solutions Ltd | Households | 2024 |
| Hybrid Vehicle Repair Ltd | Wholesale & retail | 2016 |
| Hybridan LLP | | 2007 |
| Hyde Park Developments Ltd | Construction | 2025 |
| Hyde Park Properties Limited | Real estate | 1996 |
| Hyderabad Catering UK Ltd | Hospitality | 2025 |
| Hyderco UK Limited | Professional & scientific | 1993 |
| Hyenax Limited | Professional & scientific | 2025 |
| Hyetan Ltd | Wholesale & retail | 2022 |
| Hygrade Consultants (UK) Ltd | Professional & scientific | 2002 |
| Hylands Property (HP) Limited | Extraterritorial | 2019 |
| Hyperclear UK Operations Limited | Information & communication | 2022 |
| Hyperion Business Ltd | Professional & scientific | 2015 |
| Hyperion Fit Limited | Wholesale & retail | 2020 |
| Hypervibe UK Limited | Information & communication | 2009 |
| Hypesetters UK Limited | Information & communication | 2022 |
| Hyphen Films Limited | Information & communication | 1987 |
| Hyphen Ltd | Information & communication | 2019 |
| Hypnos Properties Limited | Hospitality | 2008 |
| I & C Medical Limited | Health & social care | 2014 |
| I & C Tiling Ltd | Construction | 2020 |
| I & G Galletas Limited | Construction | 2021 |
| I & H Developments Limited | Extraterritorial | 2002 |
| I & M Finishings Ltd | Construction | 2019 |
| I & M Properties Limited | Real estate | 2013 |
| I AM Handyman Ltd | Construction | 2021 |
| I AM HER Limited | Arts & recreation | 2019 |
| I C J Consulting Ltd | Professional & scientific | 2018 |
| I E Music Limited | Other services | 1989 |
| I E Ventures Limited | Information & communication | 2018 |
| I Feier Ltd | Construction | 2020 |
| I Gate UK Ltd | Information & communication | 2024 |
| I Group Luxury Services Ltd | Professional & scientific | 2022 |
| I J Townsend Crane Tech Limited | Information & communication | 2012 |
| I Leisure Limited | Hospitality | 2013 |
| I Love SAI | Other services | 2015 |
| I Love SAI UK Limited | Other services | 2015 |
| I M H Property Management Ltd | Real estate | 2025 |
| I M Syed Ltd | Health & social care | 2019 |
| I Move U Limited | Transport & logistics | 2019 |
| I P Building Contractors Ltd | Construction | 2013 |
| I Protect Solutions Ltd | Administrative & support | 2015 |
| I Quran Ltd | Education | 2025 |
| I R Plumbing & Heating Ltd | Construction | 2015 |
| I Repair & Vape Ltd | Wholesale & retail | 2023 |
| I Shree Hair & Beauty Limited | Other services | 2024 |
| I Shree Khodiyar Ltd | Wholesale & retail | 2025 |
| I T Construction Ltd | Construction | 2017 |
| I U Services Limited | Other services | 2018 |
| I&B Utilities Ltd | Construction | 2020 |
| I&D Cleaning Ltd | Administrative & support | 2025 |
| I&D Services Ltd | Administrative & support | 2025 |
| I&F Ltd | Construction | 2021 |
| I&L Glazing Ltd | Construction | 2026 |
| I-Bcci Limited | Other services | 2025 |
| I-Mine Ltd. | Information & communication | 2019 |
| I-Qx Consulting Ltd | Information & communication | 2023 |
| I-Realty Limited | Real estate | 2012 |
| I.A Associates (London) Ltd | Professional & scientific | 2017 |
| I.M.M Construction Ltd | Construction | 2025 |
| I.N.M Construction Ltd | Construction | 2024 |
| I.P. Plumbing & Heating Ltd | Construction | 2023 |
| I.S. Trading Limited | Administrative & support | 2012 |
| I2CMEDIA Ltd | Information & communication | 2013 |
| I2S Innovation to Scale Ltd | Professional & scientific | 2026 |
| IAA Services Limited | Other services | 2004 |
| Iactea Investments Limited | Households | 2024 |
| IAH Charity Company Limited | Other services | 2011 |
| Iaid UK Ltd | Education | 2019 |
| Iamg Partners Limited | Real estate | 2016 |
| Iamtheap Limited | Information & communication | 2024 |
| IAN Constructions Ltd | Construction | 2022 |
| IAN Fitzpatrick Contracting Ltd | Construction | 2019 |
| IAN J Tait Homes Limited | Construction | 1998 |
| IAN London Limited | Construction | 2013 |
| IAN Meltzer Catering Ltd | Hospitality | 2023 |
| Ianalytics Consultancy Limited | Administrative & support | 2017 |
| Ianismatei Ltd | Transport & logistics | 2019 |
| Iaoa Limited | Health & social care | 2021 |
| IAR Services Limited | Information & communication | 2012 |
| Iaspire Care Services (Midlands) Ltd | Health & social care | 2009 |
| Iaspire Care Services Ltd | Health & social care | 2013 |
| Iatec Ltd | Construction | 2026 |