| Hunt Fitness Limited | Arts & recreation | 2018 |
| Hunta Technology Ltd | Information & communication | 2021 |
| Hunter's Garage Limited | Wholesale & retail | 2017 |
| Huqqa Garden Limited | Hospitality | 2026 |
| HW71RACING Ltd | Arts & recreation | 2026 |
| HWL Marketing Ltd | Professional & scientific | 2026 |
| Hyst Ltd | Information & communication | 2026 |
| I D Towle Limited | Construction | 2018 |
| I Need a Window Cleaner Limited | Administrative & support | 2020 |
| I Will Film Limited | Administrative & support | 2020 |
| I.G.D. Construction Ltd | Construction | 2024 |
| I.S Sweetman GUN & Rifle Makers Ltd | Manufacturing | 2017 |
| I.S. Electronics Limited | Professional & scientific | 2000 |
| IA Bespoke Limited | Other services | 2016 |
| Iain Andrews Lettings Limited | Households | 1996 |
| IAM Solutions Limited | Information & communication | 2012 |
| IAN Godbold Consultancy Ltd | Professional & scientific | 2022 |
| Iancanalitaaero Ltd | Manufacturing | 2022 |
| Iantm Ltd | Transport & logistics | 2018 |
| Ibespoke Limited | Professional & scientific | 2016 |
| Icapture Media Ltd | Information & communication | 2017 |
| Ickenham Park (South) Management Company Limited | Households | 2010 |
| Id&D Consultancy Services Ltd | Professional & scientific | 2015 |
| Ideal Property Maintenance and Building Services Limited | Construction | 2025 |
| IDK Tech Media Ltd | Information & communication | 2022 |
| Idnutu Ltd | Information & communication | 2016 |
| IG Perfect Ltd | Construction | 2021 |
| Igbunu Property Ventures Ltd | Real estate | 2019 |
| Igbunu Ventures Limited | Transport & logistics | 2014 |
| IGC Digital Limited | Professional & scientific | 2026 |
| Igolf Ltd | Arts & recreation | 2012 |
| Ihg-Uk Limited | Financial services | 2025 |
| Ikodr Limited | Information & communication | 2017 |
| IL Piccolo Limited | Hospitality | 2021 |
| ILH Technical Solutions Ltd | Professional & scientific | 2008 |
| Illan Digital Insights Ltd | Information & communication | 2024 |
| Illustrating Impact Ltd | Information & communication | 2019 |
| Imisphere Limited | Extraterritorial | 2013 |
| Impact League TCG LLP | | 2025 |
| Impact Model Cars Limited | Manufacturing | 2023 |
| Impact SIX Limited | Information & communication | 2019 |
| Imperial One Management Ltd | Real estate | 2017 |
| Improve and Consult Limited | Professional & scientific | 2016 |
| IMS Publications Ltd | Professional & scientific | 1986 |
| IN & OUT Property Renovations Ltd | Construction | 2025 |
| IN the Arena Limited | Administrative & support | 2010 |
| Inca Studios Limited | Arts & recreation | 2022 |
| INCA8 Ltd | Other services | 2020 |
| Inclusive Interactions CIC | Education | 2022 |
| Incubeats Tech Ltd | Information & communication | 2020 |
| Independent Best Interests Assessor Ltd | Health & social care | 2018 |
| Independent Fire Door Services Ltd | Public administration | 2022 |
| Independent Vehicle Rental Limited | Administrative & support | 1996 |
| Infinite Element Solutions Limited | Administrative & support | 2016 |
| Infinity House Group Limited | Construction | 2019 |
| Infinity House Holdings Ltd | Construction | 2016 |
| Infinity Retail Consultancy Limited | Professional & scientific | 2020 |
| Influential Vision Ltd | Education | 2022 |
| Inforexx Limited | Information & communication | 2009 |
| Infuntainment Limited | Information & communication | 1998 |
| Inmould Limited | Manufacturing | 1982 |
| Inside Ideas Ltd | Real estate | 2017 |
| Inspire Building Specialists Ltd | Construction | 2018 |
| Inspire Construction & Design Ltd | Construction | 2025 |
| Inspired Harmony Limited | Health & social care | 2023 |
| Inspired Mind Therapies Limited | Professional & scientific | 2017 |
| Inspirit Martial Arts Ltd | Arts & recreation | 2024 |
| Insurance Claims Professionals Ltd | Financial services | 2012 |
| Integrity Level Ltd. | Professional & scientific | 2013 |
| Integro Accountancy Limited | Professional & scientific | 2013 |
| Integro Accounting Limited | Professional & scientific | 2013 |
| Interactive Effects Ltd | Information & communication | 2021 |
| Interactive Media Services Ltd | Information & communication | 2012 |
| Interactive Property Services Ltd | Real estate | 2022 |
| Intercounty Healthcare Limited | Health & social care | 2024 |
| Interest Only Solutions Limited | Professional & scientific | 1999 |
| Interguide Group Limited | Professional & scientific | 2007 |
| Interguide Management Limited | Administrative & support | 2003 |
| Interguide Southend Limited | Real estate | 2013 |
| International Ministerial Council of Great Britain | Other services | 2010 |
| Intervl Group Ltd | Administrative & support | 2020 |
| Interweave Consulting Ltd | Information & communication | 2004 |
| Intheoffice Limited | Information & communication | 2021 |
| Intro Maritime Ltd | Wholesale & retail | 2018 |
| INV Services Ltd | Transport & logistics | 2013 |
| IO Building Automation Ltd | Construction | 2024 |
| IOL Group Limited | Construction | 2017 |
| Iredia Healthcare Ltd | Health & social care | 2025 |
| Irisense Limited | Manufacturing | 2012 |
| Irvine Property Management Limited | Professional & scientific | 2024 |
| Isavft Ltd | Administrative & support | 2022 |
| Isis Builders Limited | Construction | 1996 |
| Ismira Limited | Hospitality | 2018 |
| Ispark Digital Limited | Information & communication | 2016 |
| Istanbul of Leighton Buzzard Ltd | Hospitality | 2017 |
| IT Bits Ltd | Wholesale & retail | 2014 |
| IT Ontrack Ltd | Information & communication | 2017 |
| IT Precision Solutions Ltd | Information & communication | 2023 |
| Italiano Lofthouse Investments Ltd | Financial services | 2026 |
| Iv-Style Ltd | Transport & logistics | 2018 |