| Hollyfield House Limited | Wholesale & retail | 2009 |
| Holywood Linens Ltd | Wholesale & retail | 2022 |
| Home Plus Construction Limited | Administrative & support | 1986 |
| Home Town Self Store Limited | Professional & scientific | 2017 |
| Homerun Estates Ltd | Real estate | 2024 |
| Homes Within Reach Limited | Construction | 2026 |
| Hoppe Transport Limited | Transport & logistics | 2025 |
| Horizon Financial Coaching & Planning Limited | Professional & scientific | 2022 |
| Horizon Outsourcing Limited | Extraterritorial | 2018 |
| Horlaw Consulting Ltd | Administrative & support | 2024 |
| Horstonbridge Development Management Limited | Professional & scientific | 2010 |
| House of Liberty Ltd | Construction | 2010 |
| Housepig Investments Ltd | Real estate | 2024 |
| HOW NOW Communications Limited | Professional & scientific | 2020 |
| Howard CT (Waltham Abbey) Limited | Households | 2023 |
| Howard Kitchens & Interiors Limited | Construction | 2018 |
| Howardixon Limited | Construction | 2016 |
| Howards Construction Ltd | Construction | 2021 |
| HPL Utilities & Aggregates Ltd | Construction | 2022 |
| Hudnall Advisory Ltd | Financial services | 2019 |
| Hudnall Research Limited | Financial services | 2021 |
| Hugh C Ltd | Professional & scientific | 2024 |
| Hummingbird Insights Ltd | Professional & scientific | 2020 |
| Hurstwood Investments Limited | Real estate | 1994 |
| Hutsmith Ltd | Professional & scientific | 2020 |
| HWR Care Ltd | Health & social care | 2024 |
| Hybrid Spas Limited | Other services | 2021 |
| Hyde Electrical Services Ltd | Construction | 2010 |
| Hydroxyl Technologies Limited | Wholesale & retail | 2017 |
| IAN Crook Limited | Professional & scientific | 2021 |
| IAN Wilson Sound Limited | Administrative & support | 2009 |
| Iandaudio Ltd | Professional & scientific | 2019 |
| Ice Interior Limited | Wholesale & retail | 2007 |
| Ice Properties (London) Limited | Professional & scientific | 2003 |
| ICF Consultations Ltd | Health & social care | 2019 |
| Icml Consultancy Ltd | Professional & scientific | 2020 |
| Idcom Solutions Limited | Information & communication | 1997 |
| Ideal Corner Investment Ltd | Real estate | 2018 |
| IDO Design & Animation Limited | Information & communication | 2012 |
| Ihlgb Limited | Households | 2018 |
| IKI Talent Limited | Administrative & support | 2025 |
| IKS Locksmiths Limited | Other services | 2010 |
| IL Patio Ltd | Hospitality | 2018 |
| Ilex Court Management Limited | Administrative & support | 1991 |
| Imalogic Limited | Health & social care | 2019 |
| IMC Consultancy Ltd | Professional & scientific | 2020 |
| IMC Staff Ltd | Administrative & support | 2021 |
| IMC Tailoring Ltd | Wholesale & retail | 2009 |
| Imerso Hospitality Limited | Hospitality | 2022 |
| Imperial Coachworks Ltd | Administrative & support | 2017 |
| Imperial Vehicle Hire Berkhamsted Ltd. | Administrative & support | 2012 |
| Imperial Vehicle Hire Group Ltd | Financial services | 2023 |
| Imperial Vehicle Hire Group of Companies Ltd | Administrative & support | 2015 |
| Imperial Vehicle Hire Ltd | Administrative & support | 2025 |
| Imperial Vehicle Rentals Ltd | Administrative & support | 2014 |
| IMS Consultants Ltd | Extraterritorial | 2012 |
| IN Sinc Talent Limited | Administrative & support | 2024 |
| Incontitech Ltd | Manufacturing | 2018 |
| Independent Hire & Sales Limited | Construction | 1992 |
| Independent Scaffolding Group Limited | Construction | 2005 |
| Indigo Therapy Ltd | Health & social care | 2025 |
| Industrial Gates and Barrier Systems Ltd | Manufacturing | 2025 |
| Infinite Monkeys Limited | Information & communication | 2018 |
| Infinity Employment Ltd | Administrative & support | 2023 |
| Influxar Limited | Information & communication | 2026 |
| Informed Decisions (Analytics) Limited | Professional & scientific | 2015 |
| Infrastructure Enhancement Limited | Administrative & support | 2013 |
| Infusion Group Ltd | Other services | 2019 |
| Inland Waterways Association(The) | Other services | 1958 |
| Inland Waterways Enterprises Limited | Wholesale & retail | 2016 |
| Innochem UK Ltd | Manufacturing | 2024 |
| Inside Matters Design Ltd | Professional & scientific | 2021 |
| Insight Market Place Services Limited | Information & communication | 2015 |
| Insight Retail Group Limited | Information & communication | 1996 |
| Insight Retail Ltd | Wholesale & retail | 2005 |
| Instrumentals Club Ltd | Wholesale & retail | 2024 |
| Intech Works Limited | Information & communication | 2003 |
| Intelligent Sanctuary Ltd | Information & communication | 2017 |
| Intent Marine Ltd | Administrative & support | 2023 |
| Interim Management Solutions Limited | Extraterritorial | 2012 |
| International Federation of Audit Bureaux of Certification | Other services | 2021 |
| International Forest Industries Ltd | Information & communication | 2007 |
| International Mining Events Ltd | Information & communication | 2011 |
| Interzone Investments Ltd | Financial services | 2021 |
| Intowork Software Limited | Information & communication | 2020 |
| IOW Property Staging Ltd | Professional & scientific | 2026 |
| Ioyou Prods Limited | Education | 2019 |
| IRD Recruitment Ltd | Administrative & support | 2025 |
| Ironage Developments Limited | Administrative & support | 2001 |
| Isaiah 3218 Properties Ltd | Households | 2026 |
| Isio Estates Ltd | Administrative & support | 2026 |
| Isotope Agency Ltd | Professional & scientific | 2026 |
| Isotope Capital Limited | Financial services | 2016 |
| IT Business Finance Limited | Extraterritorial | 2007 |
| It's Just Stuff Limited | Extraterritorial | 2021 |
| ITS on Hold Limited | Real estate | 2015 |
| ITS21 Ltd | Information & communication | 2018 |
| Ivanhoe Resourcing Limited | Administrative & support | 2014 |
| IVF Professionals Ltd | Administrative & support | 2016 |
| IW Properties Ltd | Real estate | 2019 |