| Hurstwood Sports Group Ltd | Arts & recreation | 2025 |
| Huxleysporting Ltd | Wholesale & retail | 2025 |
| HV Horticulture Limited | Wholesale & retail | 1987 |
| HW Cleaning Ltd | Administrative & support | 2021 |
| Hybrock Space Logistics Group Ltd | Transport & logistics | 2026 |
| Hydda Limited | Construction | 2007 |
| Hydro Paws Limited | Professional & scientific | 2015 |
| Hyrule Properties Limited | Real estate | 2022 |
| Hywel Hughes Commercial Property Consultants Limited | Professional & scientific | 2011 |
| I 2 I Media Limited | Information & communication | 2002 |
| I Care for the Elderly Ltd | Information & communication | 2016 |
| I D O Cosults Ltd | Information & communication | 2019 |
| I Fit Fires & Flues Ltd | Construction | 2014 |
| I&M Associates Ltd | Transport & logistics | 2025 |
| I-Pcg Ltd | Construction | 2023 |
| I2IC Ltd | Information & communication | 2021 |
| IAG Broking Limited | Transport & logistics | 2001 |
| IAG Holdings Limited | Real estate | 1998 |
| IAN Chisholm Limited | Administrative & support | 2006 |
| IAN Hatton Motorcycles Limited | Wholesale & retail | 2004 |
| IAN Holden Aviation Consultancy Ltd | Transport & logistics | 2018 |
| Ibeab Holdings Ltd | Real estate | 2025 |
| Iberiansun Limited | Administrative & support | 2023 |
| IC Trading Ltd. | Wholesale & retail | 2015 |
| Ice Benevolent Fund | Other services | 2008 |
| Icehope Limited | Households | 1986 |
| Icme Consultants Ltd | Professional & scientific | 2014 |
| Iconic Brows and Beauty Limited | Other services | 2024 |
| ID Transnational Consultancy Limited | Professional & scientific | 2015 |
| Ideas in Food Limited | Professional & scientific | 2023 |
| Ideias Design Agency Limited | Professional & scientific | 2023 |
| Identek Global Search Ltd | Administrative & support | 2017 |
| Identity Design & Creative Limited | Professional & scientific | 2012 |
| Identity Incorporated Group Limited | Professional & scientific | 2012 |
| IDL Media Ltd | Information & communication | 2025 |
| Idlerock Property Investment Ltd | Real estate | 2021 |
| IDS Autoworks Limited | Wholesale & retail | 2025 |
| Igaming Core Events Ltd | Professional & scientific | 2025 |
| Igaming Core Ltd | Professional & scientific | 2024 |
| Igloo Media Ltd | Information & communication | 2018 |
| Ignite Fitness Coaching Limited | Arts & recreation | 2020 |
| IGS Logistics Ltd | Transport & logistics | 2012 |
| IKE Consulting Ltd | Professional & scientific | 2022 |
| Ilios Sports Management Limited | Arts & recreation | 2025 |
| Illa Ironing Limited | Other services | 2014 |
| Illuminate HR Ltd | Administrative & support | 2025 |
| Illustris UK Ltd | Construction | 2018 |
| Images on Line Limited | Administrative & support | 2000 |
| Imanage Homes Ltd | Real estate | 2020 |
| Imanage Performance Limited | Education | 2003 |
| Imita Limited | Professional & scientific | 2019 |
| Imogen's Aesthetics Limited | Other services | 2019 |
| Impact Design Engineering Limited | Professional & scientific | 1997 |
| Impact Integrations Ltd | Information & communication | 2025 |
| Imperial Buildings (Horley) Limited | Real estate | 1959 |
| IMS Cloud Ltd | Information & communication | 2018 |
| IMS Computing Ltd | Information & communication | 2009 |
| Imt&E Ltd | Other services | 2023 |
| IN a Box Records Limited | Information & communication | 2016 |
| In-House Residence Ltd | Construction | 2022 |
| Inasus UK Ltd | Construction | 2010 |
| Inchange Ltd | Professional & scientific | 2021 |
| Inciem Technologies Limited | Information & communication | 2025 |
| Inclusive Speech Rights Initiative UK Limited | Information & communication | 2026 |
| Incor Group Limited | Professional & scientific | 2017 |
| Incor Group Management Limited | Administrative & support | 2006 |
| Independent Lifestyles Homes Ltd | Extraterritorial | 2006 |
| Independent Pilots' Association | Other services | 1992 |
| Independent Success Systems Limited | Administrative & support | 2007 |
| Indianfood to Enjoy Ltd | Hospitality | 2017 |
| Indigo Lane Recruitment Limited | Administrative & support | 2009 |
| Indios Foods Ltd | Manufacturing | 2020 |
| Indybikes Ltd | Wholesale & retail | 2020 |
| Infiniium Limited | Professional & scientific | 2025 |
| Infinite Landscaping Ltd | Administrative & support | 2023 |
| Infinite Plumbing and Heating Ltd | Construction | 2017 |
| Infinity Accounting Solutions Limited | Professional & scientific | 2015 |
| Infinity Floors Limited | Construction | 2021 |
| Infinity Food TAG Ltd | Manufacturing | 2025 |
| Infinity Massage Therapy Limited | Other services | 2023 |
| Influ Limited | Administrative & support | 2015 |
| Information Architecture Limited | Information & communication | 2017 |
| Infotek Software Ltd | Information & communication | 2004 |
| Infrastructure Performance Group Ltd | Professional & scientific | 2026 |
| Ingenious Alchemy Company Limited | Professional & scientific | 1959 |
| Ingle Properties Ltd | Real estate | 2023 |
| Inglewood Partners Limited | Professional & scientific | 2019 |
| Ingot Consultancy Ltd | Professional & scientific | 2022 |
| Initiative Surf Ltd | Arts & recreation | 2011 |
| Inkie Limited | Information & communication | 2023 |
| Innovapp Design Ltd | Information & communication | 2012 |
| Insight Futures Limited | Real estate | 2017 |
| Insight Video Marketing Limited | Professional & scientific | 2019 |
| Insightful Ideas Limited | Information & communication | 2023 |
| Inspire Confidence Ltd | Professional & scientific | 2024 |
| INSURE4NATURE Limited | Financial services | 2023 |
| Intelligent Valves Ltd | Energy | 2021 |
| Intelliquest Ltd | Information & communication | 2025 |
| Inter County Insurance Services Limited | Financial services | 2007 |
| Inter Vivos Digital Marketing Ltd | Professional & scientific | 2017 |