| Hydrohub Mechanical Ltd | Construction | 2025 |
| Hyena Overland UK Limited | Wholesale & retail | 2025 |
| Hygiena International Limited | Wholesale & retail | 2001 |
| Hygiene Hands Limited | Health & social care | 2021 |
| Hyper Bazaar Group Ltd | Wholesale & retail | 2025 |
| Hyper Bazar Distributions Ltd | Wholesale & retail | 2025 |
| Hyper Grand Bazaar Ltd | Wholesale & retail | 2024 |
| Hyper Motors Ltd | Administrative & support | 2023 |
| Hyper Targeted Marketing Limited | Information & communication | 2019 |
| Hyper Wholesale Ltd | Wholesale & retail | 2024 |
| Hyperactive Broadcast Limited | Information & communication | 1985 |
| Hyperactive Property Limited | Information & communication | 2015 |
| HYPO21 Ltd | Wholesale & retail | 2021 |
| Hypopharma Ltd | Wholesale & retail | 2021 |
| Hyrule Ltd | Information & communication | 2018 |
| I & E Builders Ltd | Construction | 2018 |
| I & S Property Group Limited | Construction | 2019 |
| I AM Genius Business Ltd | Information & communication | 2021 |
| I AM NOT a Solicitor Limited | Extraterritorial | 2011 |
| I B Innovation Limited | Construction | 2022 |
| I Bill U Limited | Extraterritorial | 2011 |
| I on Costs Limited | Information & communication | 2015 |
| I on U Limited | Information & communication | 2015 |
| I P (Project & Commercial Management) Limited | Professional & scientific | 2023 |
| I Q Aluminium Systems Ltd | Manufacturing | 2024 |
| I S Fazal Ltd | Professional & scientific | 2023 |
| I Sept Ltd | Wholesale & retail | 2018 |
| I Tutor Club Ltd | Education | 2024 |
| I&D Brickwork Ltd | Construction | 2018 |
| I&D Estates Ltd | Construction | 2023 |
| I&D Ltd | Construction | 2008 |
| I&I Developers Limited | Real estate | 2024 |
| I&I Express Logistics Ltd | Transport & logistics | 2025 |
| I&Z Carpentry Ltd | Construction | 2013 |
| I-Can Support Group C.I.C. | Education | 2021 |
| I-Free Worldwide Limited | Administrative & support | 2004 |
| I-Serv Consulting International Ltd | Information & communication | 2019 |
| I. & B. Records Limited | Wholesale & retail | 1978 |
| I.Insights Ltd | Information & communication | 2023 |
| I2 Analytical Limited | Professional & scientific | 2003 |
| I2A Limited | Professional & scientific | 2013 |
| I2C Limited | Administrative & support | 2006 |
| IA Driving School Ltd | Education | 2021 |
| IA Properties Watford Ltd | Real estate | 2023 |
| IA Quants Build Limited | Professional & scientific | 2025 |
| IAN Abrey Limited | Professional & scientific | 2010 |
| IAN C Brown Limited | Professional & scientific | 2014 |
| IAN Wright Associates Limited | Professional & scientific | 2001 |
| Ianos Ltd | Information & communication | 2012 |
| IAR Joinery Limited | Manufacturing | 2015 |
| IAS Investment Arms Limited | Financial services | 2026 |
| IAZ Limited | Professional & scientific | 2016 |
| Iaza Medicals Ltd | Wholesale & retail | 2024 |
| Ibaiza Ltd | Wholesale & retail | 2025 |
| Ibarra Associates Limited | Administrative & support | 2020 |
| Ibbitc Limited | Transport & logistics | 2015 |
| Ibmb Building Ltd | Construction | 2025 |
| Ibn.A Limited | Professional & scientific | 2017 |
| Ibox Local Limited | Professional & scientific | 2019 |
| IBS Cleaning Services Limited | Administrative & support | 2019 |
| Ibsa Pharma Limited | Wholesale & retail | 2000 |
| Ibusiness Technologies Limited | Information & communication | 2002 |
| IC Concrete Pumping Ltd | Construction | 2019 |
| IC Property Investors Limited | Real estate | 2019 |
| Icarequick Ltd | Health & social care | 2020 |
| Ice Cream Tree Ltd | Information & communication | 2026 |
| Ichor Networking Ltd | Information & communication | 2015 |
| Ichthus Consulting and Training Ltd | Information & communication | 2013 |
| Iconic Beauty Salon Limited | Other services | 2024 |
| Icopy Ltd | Administrative & support | 2018 |
| ICS Technical and Services Ltd | Administrative & support | 2016 |
| ICW Powermode Limited | Professional & scientific | 2003 |
| ID Estates (LH) Limited | Real estate | 2016 |
| ID Estates Limited | Construction | 2003 |
| ID Housing Construction Ltd | Real estate | 2015 |
| Idarah Maruf Britain Limited | Education | 2006 |
| Iday Limited | Education | 2019 |
| Ideai Ltd | Education | 2018 |
| Ideal Carpentry & Building Solutions Ltd | Construction | 2023 |
| Ideal Europe Limited | Wholesale & retail | 1993 |
| Ideal Glass W Limited | Construction | 2024 |
| Ideal View Electrical Ltd | Construction | 2026 |
| Ideal View Technical Limited | Construction | 2023 |
| Idealacrea Residents Management Limited | Households | 1987 |
| Idealogic Ltd | Information & communication | 2023 |
| IDH Estates and Developments Limited | Construction | 2013 |
| Idmg Limited | Transport & logistics | 2013 |
| IEG Installation Ltd | Construction | 2017 |
| IF1 Services Limited | Professional & scientific | 2023 |
| Ifeco Global Motors Limited | Wholesale & retail | 2023 |
| Ifes UK Ltd | Information & communication | 2016 |
| IG3 Construction Ltd | Construction | 2023 |
| IGD Limited | Professional & scientific | 2022 |
| IGD Services Limited | Information & communication | 1997 |
| IGD Trading Limited | Extraterritorial | 2019 |
| Igloo.Co.Uk Limited | Professional & scientific | 2004 |
| Ignatis Ltd | Information & communication | 2016 |
| Ignite Academy Ltd | Professional & scientific | 2024 |
| Ignite Enterprises Ltd | Financial services | 2013 |
| Ignite Estates Ltd | Real estate | 2024 |