| Hussars Charge Ltd | Transport & logistics | 2019 |
| Husteds Care Ltd | Health & social care | 2015 |
| Hutchinson Engineering Solutions Limited | Professional & scientific | 2007 |
| Hvac Heating Services Ltd | Professional & scientific | 2020 |
| Hvvm Holdings Ltd | Health & social care | 2018 |
| Hwith Holidays Ltd | Hospitality | 2021 |
| HWT Transport Services Limited | Transport & logistics | 2019 |
| Hyaci Ltd | Wholesale & retail | 2024 |
| Hybrid Training Hub Ltd | Arts & recreation | 2024 |
| Hybrit Connect Ltd | Wholesale & retail | 2026 |
| Hyderabadi Bandi Ltd | Hospitality | 2026 |
| Hyderabadi Food & More Limited | Hospitality | 2026 |
| Hydrate UK Ltd | Administrative & support | 2025 |
| Hydropeat Limited | Professional & scientific | 2001 |
| Hydrorace Limited | Wholesale & retail | 2016 |
| Hygienic Finishes ( South) Ltd | Construction | 2015 |
| Hyland Ventures Ltd | Wholesale & retail | 2025 |
| Hypeflow Ltd | Wholesale & retail | 2026 |
| Hyperform Video Limited | Arts & recreation | 2021 |
| I & F Medical Consultancy Ltd | Health & social care | 2022 |
| I & G (Lodge Yard) Ltd | Other services | 2021 |
| I a Glenister Electrical Engineers (Aylesbury) Ltd | Construction | 2012 |
| I AM Junior Production Limited | Information & communication | 2024 |
| I FIX Heating Limited | Construction | 2021 |
| I J Parsons Limited | Construction | 2003 |
| I K W (Business Consultancy) Limited | Administrative & support | 1993 |
| I MOP Clean Ltd | Real estate | 2011 |
| I Run Like a Girl Ltd | Administrative & support | 2026 |
| I&K Prestige Food Ltd | Wholesale & retail | 2012 |
| I-X Trade Ltd | Wholesale & retail | 2026 |
| I.M Plumbing Heating and GAS Ltd | Construction | 2026 |
| I.N & Co Developments Ltd | Manufacturing | 2021 |
| IA Operations Ltd | Professional & scientific | 2023 |
| IAG Technology Limited | Manufacturing | 2002 |
| IAN Davis Construction Limited | Construction | 2024 |
| IAN Webb Engineering Limited | Manufacturing | 2002 |
| IAQ Filtration Ltd | Manufacturing | 2019 |
| Iasmina Express Ltd | Transport & logistics | 2026 |
| Ibart Ltd | Construction | 2017 |
| Ibza Ltd | Wholesale & retail | 2025 |
| Icatching Design Limited | Information & communication | 2002 |
| ICB Enterprise Ltd | Professional & scientific | 2020 |
| Ice Delivery Company UK Limited | Other services | 2025 |
| ICJ Services Ltd | Construction | 2026 |
| Ickford Convenience Stores Ltd | Wholesale & retail | 2018 |
| Ickford Learning Trust | Education | 2016 |
| Iconcept Construction UK Ltd | Construction | 2024 |
| ICRE8DESIGN Limited | Extraterritorial | 2004 |
| ICY Bananas Limited | Information & communication | 2022 |
| Ideaflo Limited | Information & communication | 2024 |
| Idealab 3D Print Ltd | Wholesale & retail | 2025 |
| Identify Networks Limited | Professional & scientific | 2008 |
| Identity Solved Ltd | Information & communication | 2025 |
| IDO the Country Wedding Company LLP | | 2014 |
| Idomit Agro Ltd | Wholesale & retail | 2025 |
| Idoor Limited | Construction | 2019 |
| Idsource Ltd | Construction | 2016 |
| Iestimate Ltd | Professional & scientific | 2024 |
| IFC Advisory Ltd | Professional & scientific | 2014 |
| Iflourish Leadership Limited | Professional & scientific | 2026 |
| Igetmaths Ltd | Professional & scientific | 2013 |
| Igma Construction Ltd | Construction | 2016 |
| Ignite ADS Ltd | Information & communication | 2025 |
| Ignite Automotive Ltd | Wholesale & retail | 2021 |
| Ignite Brands Ltd | Professional & scientific | 2020 |
| Ignite DCT and Engine Services Ltd | Wholesale & retail | 2022 |
| Ignite GAS Solutions Ltd | Construction | 2023 |
| Ignitely Innovations Ltd | Information & communication | 2025 |
| Ignition Strategy Ltd | Professional & scientific | 2023 |
| IGT Associates Ltd | Real estate | 2016 |
| IHF Services Ltd | Real estate | 2015 |
| Ihome Improvement Limited | Construction | 2017 |
| Ihomedecoration Limited | Construction | 2012 |
| IJF Homes Limited | Extraterritorial | 2024 |
| Ikdecore Limited | Arts & recreation | 2025 |
| Iketina Limited | Health & social care | 2013 |
| Ilchev Limited | Wholesale & retail | 2015 |
| ILD Electrical Limited | Construction | 2016 |
| Illicit Clothing Ltd | Wholesale & retail | 2017 |
| Ilu-London Limited | Manufacturing | 2024 |
| IM Solutions Limited | Professional & scientific | 2006 |
| Image Pine Furniture Limited | Real estate | 1994 |
| Imagelane Ltd | Transport & logistics | 2019 |
| Imagevet UK Ltd | Professional & scientific | 2021 |
| Imaginarium Limited | Information & communication | 2010 |
| Imaginations Group Ltd | Information & communication | 2023 |
| Imaginists Limited | Professional & scientific | 2023 |
| Imaritech Ltd | Information & communication | 2018 |
| Imbolc Limited | Information & communication | 2016 |
| Imbrovschi Limited | Health & social care | 2025 |
| Immaculately Clean Limited | Administrative & support | 2025 |
| Immersif Co. Ltd | Professional & scientific | 2024 |
| Impact 21 Limited | Professional & scientific | 2016 |
| Impact Drywall Ltd | Construction | 2023 |
| Impact Property Group (Aylesbury) Ltd | Real estate | 2023 |
| Impact Property Group Ltd | Real estate | 2018 |
| Impact Public Relations Ltd | Professional & scientific | 2021 |
| Impact Sign Solutions Ltd | Manufacturing | 2006 |
| Impactful Women Ltd | Professional & scientific | 2025 |
| Impetus UK Limited | Professional & scientific | 1998 |