| Horses of Cappadocia Limited | Wholesale & retail | 2023 |
| Hortiserv Ltd | Agriculture & fishing | 2020 |
| Houghton Mews (Luton) Limited | Real estate | 1989 |
| Houghton Phillips Limited | Administrative & support | 2002 |
| Hour Hands Ltd | Administrative & support | 2015 |
| House of Fina Ltd | Other services | 2025 |
| HOY Holdings Limited | Real estate | 2020 |
| HPB Properties Limited | Real estate | 2017 |
| Hpgmkg Property Limited | Real estate | 2020 |
| HPO Clinic Limited | Health & social care | 2024 |
| HPO Fitness Limited | Arts & recreation | 2021 |
| Hrfc Supporters Limited | Arts & recreation | 2017 |
| Hudson Shribman Limited | Administrative & support | 2018 |
| Hugga Mugga Ltd | Information & communication | 1998 |
| Hugo Jasper Research and Management Ltd | Professional & scientific | 2017 |
| Humane Design Ltd | Information & communication | 2004 |
| Hummingbird Office Solutions Limited | Administrative & support | 2017 |
| Hunter Worldwide Limited | Manufacturing | 2001 |
| Hurleys Home Renovations Ltd | Construction | 2025 |
| Husnara Begum Consulting Limited | Professional & scientific | 2013 |
| Husnara Begum Property Ltd | Real estate | 2021 |
| Hygenika Ltd | Health & social care | 2020 |
| Hypergen Ltd | Manufacturing | 2019 |
| Hyperion Global Limited | Professional & scientific | 2014 |
| I Heart Hemp C.I.C. | Manufacturing | 2017 |
| I John Consulting Limited | Professional & scientific | 2013 |
| I-Audit Services Ltd | Professional & scientific | 2000 |
| I-Financial Services Group Limited | Financial services | 1996 |
| I-Financial Services Limited | Extraterritorial | 2000 |
| I-Insurance Services Ltd | Professional & scientific | 2000 |
| I-Legal Services Limited | Extraterritorial | 2001 |
| I-Payroll Services Limited | Extraterritorial | 2000 |
| I-Surfer Consulting Limited | Information & communication | 2021 |
| I-Taxation Services Limited | Extraterritorial | 2000 |
| IA FD Services Ltd | Administrative & support | 2016 |
| Iain C Conn & Associates Limited | Professional & scientific | 2020 |
| Iain Ross & Co Limited | Information & communication | 2006 |
| Ibook IT Ltd | Other services | 2025 |
| Ibuiltnapp Limited | Information & communication | 2026 |
| ICA Technology Limited | Information & communication | 2020 |
| Iceberg Accounting Limited | Professional & scientific | 2014 |
| Iceberg Consultancy Limited | Extraterritorial | 2014 |
| Icknield Instruments Limited | Professional & scientific | 2015 |
| Icon Cleaning Ltd | Administrative & support | 2025 |
| Iconic Bespoke Vehicle Operations Ltd | Wholesale & retail | 2017 |
| Identity Therapies Limited | Health & social care | 2025 |
| IFX Specialty Limited | Financial services | 2024 |
| IGM Plumbing, Heating & Leak Detection Limited | Construction | 2023 |
| Ignition Accounting Limited | Professional & scientific | 2019 |
| Ignition Growth Services Limited | Administrative & support | 2012 |
| Ignitioncfo Limited | Professional & scientific | 2020 |
| Iheart Principles Limited | Education | 2016 |
| Ihlosi Imports Ltd | Wholesale & retail | 2019 |
| Iksystems Limited | Information & communication | 2012 |
| Iksystems-Investments Ltd | Wholesale & retail | 2020 |
| Ilcapo Properties Limited | Real estate | 2023 |
| Ilovevillasglobal Ltd | Information & communication | 2023 |
| IM Financial Services Group Ltd | Financial services | 2024 |
| Image Architecture Limited | Professional & scientific | 2003 |
| Immanuel International Group Ltd | Real estate | 2022 |
| Immersive Walkthroughs Limited | Professional & scientific | 2025 |
| Impact Central Limited | Professional & scientific | 2019 |
| Impact Factory Limited | Education | 2005 |
| Impala Garden Rooms Limited | Construction | 2020 |
| Impala Property Ventures Limited | Construction | 2013 |
| Inaa's International Limited | Wholesale & retail | 2022 |
| Inaa's Limited | Information & communication | 2019 |
| Incandescent Technologies U.K. Ltd | Information & communication | 2013 |
| Inconstruct Services Ltd | Construction | 2016 |
| Incubate (2016) Ltd | Professional & scientific | 2016 |
| Incupia Ltd | Information & communication | 2011 |
| Indach Coaching and Wellness Ltd | Health & social care | 2024 |
| Indi Markets Ltd | Professional & scientific | 2026 |
| India Slater Ltd. | Professional & scientific | 2022 |
| Indysust Limited | Professional & scientific | 2026 |
| Infogain Limited | Administrative & support | 2013 |
| Innate Health Limited | Real estate | 2007 |
| Innovation & Sustainability Limited | Professional & scientific | 2021 |
| Innovation Precision Machining Ltd | Manufacturing | 2024 |
| Innwestate Ltd | Real estate | 2024 |
| Insight Financial Research Limited | Financial services | 2007 |
| INT Consultants Ltd | Construction | 2024 |
| Intaglio Mentoring Limited | Health & social care | 2023 |
| Intalec Property Limited | Real estate | 2014 |
| Intech Blinds Ltd | Other services | 2025 |
| Intelegon UK Ltd | Information & communication | 2020 |
| Interface CMS Limited | Administrative & support | 2011 |
| Interface Planning & Development Management Limited | Professional & scientific | 2023 |
| Intrinsic Value Real Estate Advisers Limited | Professional & scientific | 2018 |
| Intrinsic Values Limited | Professional & scientific | 2003 |
| Invent - UK Limited | Construction | 1988 |
| Inyati Consulting Ltd | Professional & scientific | 2018 |
| IOKN2BOK Clothing Limited | Other services | 2021 |
| IQ Furniture Limited | Wholesale & retail | 2016 |
| Iris Close Residents Company Limited | Real estate | 2013 |
| Iron Horse Capital (UK) Limited | Construction | 2024 |
| Irrelephant Games Limited | Manufacturing | 2025 |
| Irvine IT Limited | Information & communication | 2012 |
| IT Security Locksmith Limited | Administrative & support | 2023 |
| Itera Services Ltd | Administrative & support | 2026 |