| Houses of Hope Care Group Ltd | Health & social care | 2018 |
| Howhigh Roofing Limited | Construction | 2021 |
| HQ Real Estate Limited | Real estate | 2018 |
| HSA Abodes Ltd | Real estate | 2024 |
| Humangeni Limited | Professional & scientific | 2018 |
| Humble Construction Ltd | Construction | 2024 |
| Hunjan Properties Ltd | Real estate | 2017 |
| Hurst Priors Ltd | Real estate | 2025 |
| Hynes Builders Ltd | Construction | 2020 |
| HYP Estates Ltd | Real estate | 2023 |
| HZ Management London Ltd | Arts & recreation | 2024 |
| I Heat & Plumb Limited | Construction | 2013 |
| I Heat and Cool Ltd | Construction | 2024 |
| I.M Hawken Limited | Manufacturing | 2018 |
| IAS Rentals Ltd | Real estate | 2026 |
| IAU Eacademy Ltd | Education | 2021 |
| Ice Homes Limited | Real estate | 2025 |
| Icon Kitchen Designs Ltd | Professional & scientific | 2019 |
| Icona Asset Management Ltd | Real estate | 2018 |
| Icona Holdings Limited | Real estate | 2017 |
| Icona Homes Limited | Construction | 2007 |
| Iculus Ltd | Real estate | 2018 |
| Ideanodes Ltd | Education | 2025 |
| Identifyou Technologies (OPC) Private Limited | Information & communication | 2024 |
| Identity Productions Ltd | Wholesale & retail | 2010 |
| Idex Construction Ltd | Construction | 2007 |
| IDM and Infosec Solutions Ltd | Information & communication | 2011 |
| Idrive Recruitment Ltd | Transport & logistics | 2019 |
| IGO Holding Group Ltd | Financial services | 2022 |
| Ihsan Surgery Ltd | Health & social care | 2025 |
| IKO 16 Ltd | Construction | 2016 |
| Illummerse Limited | Information & communication | 2022 |
| Image Carpets Limited | Wholesale & retail | 2002 |
| Imleya House Technologies Limited | Information & communication | 2008 |
| Immobix Limited | Real estate | 2024 |
| Impact Mission AI Ltd | Wholesale & retail | 2026 |
| Impact Mission Ltd | Information & communication | 2025 |
| Imperial Legal Services Limited | Professional & scientific | 2015 |
| Improve Your Health Ltd | Health & social care | 2014 |
| Improve Your Living Limited | Real estate | 2017 |
| IMX Management and Consulting Group Ltd | Professional & scientific | 2026 |
| Indigo Toucan Limited | Information & communication | 2014 |
| Infinity Coffee Shop Ltd | Hospitality | 2025 |
| Infinity Homes and Developments Ltd | Real estate | 2016 |
| Infocube Limited | Information & communication | 2026 |
| Infusion Village Limited | Hospitality | 2022 |
| Inhuman Race Ltd | Wholesale & retail | 2020 |
| Inka Properties Limited | Real estate | 2009 |
| Inkleby Media Limited | Information & communication | 2015 |
| Innovation Engine Limited | Information & communication | 2015 |
| Inosa Health Ltd | Health & social care | 2026 |
| INP Engineering & Services UK Ltd | Professional & scientific | 2018 |
| Insights-Digital Ltd | Wholesale & retail | 2025 |
| Insiyt Limited | Information & communication | 2025 |
| Inspire Property Investments Limited | Real estate | 2003 |
| Instyle Studios Surrey Ltd | Arts & recreation | 2025 |
| Intelligent Home Online Ltd | Wholesale & retail | 2009 |
| Interbrosis Corporation Limited | Administrative & support | 2022 |
| Intergest United Kingdom Limited | Professional & scientific | 1987 |
| International Actuarial Consultants Limited | Financial services | 2016 |
| International Graduates Services Limited | Information & communication | 2010 |
| International Medical Health Organisation | Health & social care | 2010 |
| Interpalm Group Limited | Financial services | 2003 |
| Intym Services Limited | Transport & logistics | 2025 |
| Inventory PAL Ltd | Households | 2023 |
| Inyura Enterprise Ltd | Wholesale & retail | 2017 |
| IOT Integration Limited | Information & communication | 2023 |
| IR Property Trading Ltd | Real estate | 2026 |
| Irmscher (UK) Limited | Wholesale & retail | 1987 |
| ISA45 Energy & Investment Group UK Ltd | Mining & quarrying | 2024 |
| Isabella Beauty Ltd | Other services | 2023 |
| Isara Ltd | Information & communication | 2023 |
| Isfera Limited | Health & social care | 2022 |
| Isharp Limited | Information & communication | 2010 |
| Isla's Studio Ltd | Arts & recreation | 2026 |
| Ispira Ltd | Professional & scientific | 2002 |
| It's Thecha Bristol Limited | Hospitality | 2026 |
| It's Thecha Canary Wharf Limited | Hospitality | 2026 |
| It's Thecha Canning Town Limited | Hospitality | 2026 |
| It's Thecha Limited | Hospitality | 2026 |
| It's Thecha Manchester Limited | Hospitality | 2026 |
| Itech Innovators Ltd | Professional & scientific | 2025 |
| IZA Services Limited | Information & communication | 2015 |
| J Field Group Ltd | Wholesale & retail | 2019 |
| J.A.E. Building Ltd | Construction | 2018 |
| J.K.S.S. Properties Ltd | Real estate | 2020 |
| Jaffco Ltd | Wholesale & retail | 2022 |
| Jags Management Ltd | Professional & scientific | 2019 |
| Jaiya Limited | Construction | 2019 |
| James Plumbing Ltd | Construction | 2026 |
| Jarp Software Limited | Information & communication | 2023 |
| JAS Resources & Consultancy Ltd | Real estate | 2019 |
| Jayanth Ltd | Health & social care | 2009 |
| JBK Investments Limited | Real estate | 2011 |
| JC Web Solutions Ltd | Information & communication | 2015 |
| JD Truong Limited | Professional & scientific | 2023 |
| JDK Enterprise Solutions Ltd | Transport & logistics | 2023 |
| Jedi Property Solutions Limited | Real estate | 2002 |
| Jeykand Ltd | Hospitality | 2024 |
| Jhon Brok Limited | Wholesale & retail | 2026 |