| Hydrolex Ltd | Professional & scientific | 2025 |
| Hystel Limited | Real estate | 1947 |
| I & J Supplies Limited | Wholesale & retail | 2015 |
| I & L Autos Limited | Wholesale & retail | 2023 |
| I & M Trading Limited | Financial services | 2019 |
| I AM SJM Limited | Manufacturing | 2024 |
| I Drive U Ltd | Transport & logistics | 2005 |
| I Want Noise Ltd | Arts & recreation | 2025 |
| I-Nomi.Net Limited | Information & communication | 2014 |
| I-Procaas Limited | Information & communication | 2018 |
| I.T. ME Resolve Ltd | Information & communication | 2019 |
| Iaplus Limited | Administrative & support | 2011 |
| Iatro Tech Ltd | Construction | 2017 |
| IBT Services (Southern) Limited | Water & waste | 2012 |
| ICA Electrical Contractors Limited | Construction | 2002 |
| Ice Cream Creative Ltd | Professional & scientific | 2025 |
| Icpav Presentation Services Limited | Professional & scientific | 2014 |
| ID London Limited | Administrative & support | 2009 |
| Id&T Solutions Limited | Administrative & support | 2024 |
| Ideal Care Solutions Ltd | Administrative & support | 2025 |
| Ideal Carpentry and Design Limited | Manufacturing | 2021 |
| Ideal Cars Sussex Limited | Wholesale & retail | 2016 |
| Ideal Resort Limited | Construction | 2022 |
| IDM Building Services Limited | Construction | 2004 |
| Idma Limited | Information & communication | 2021 |
| Idris Express Ltd | Transport & logistics | 2024 |
| Ifzw - Maintenance Limited | Manufacturing | 2005 |
| Ignis Wellbeing Ltd | Arts & recreation | 2025 |
| Ignite Business Results Limited | Other services | 1994 |
| Ignite Purpose UK Limited | Professional & scientific | 2023 |
| IHM Property Limited | Real estate | 2000 |
| Ikigai Global Communications Ltd | Professional & scientific | 2024 |
| Ikos RAS Limited | Real estate | 2013 |
| Ilande Limited | Information & communication | 2012 |
| Ilash Mania Ltd | Wholesale & retail | 2025 |
| Iles Formula UK Limited | Wholesale & retail | 2024 |
| Imagine Engine Ltd | Information & communication | 2024 |
| Immersus Audio Ltd | Manufacturing | 2023 |
| Impact Communicate Limited | Administrative & support | 2009 |
| Impact Construction Consultants Limited | Professional & scientific | 2019 |
| Impact Money Group Limited | Financial services | 2017 |
| Impact Performance Ltd | Wholesale & retail | 2025 |
| Impact SF Packaging Limited | Other services | 1991 |
| Impact Specialist Finance Limited | Financial services | 2002 |
| Impact Supply Chain Solutions Limited | Professional & scientific | 2020 |
| Imperium Aviation Services Ltd | Professional & scientific | 2021 |
| IN My Garden Room Ltd | Construction | 2026 |
| IN Partnership Financial Advisers Limited | Financial services | 2006 |
| In-Still Consulting Ltd | Professional & scientific | 2013 |
| INBOUND360 Ltd | Information & communication | 2013 |
| Inchogo Ltd | Wholesale & retail | 2022 |
| Inco Surveys Ltd | Professional & scientific | 2017 |
| Incognito Property Ltd | Real estate | 2018 |
| Indefinite Films Limited | Information & communication | 2009 |
| Independent Migrant Services Ltd | Health & social care | 2023 |
| Indexsar Ltd | Information & communication | 2009 |
| India Woven Travel Ltd | Administrative & support | 2020 |
| Indigo & Limited | Information & communication | 2015 |
| Indigo Tax & Accountancy Limited | Professional & scientific | 2003 |
| Inebriation Group Ltd | Financial services | 2025 |
| Inebriation Ltd | Manufacturing | 2020 |
| Ineedtech Ltd | Information & communication | 2021 |
| Inferno Knight Ltd | Wholesale & retail | 2026 |
| Infinitrip Ltd | Information & communication | 2025 |
| Infinity Aviation Training Ltd | Professional & scientific | 2018 |
| Infinity Estate Investments Ltd | Real estate | 2018 |
| Infinity Greetings Ltd | Wholesale & retail | 2019 |
| Infinity Gymnastics CIC | Arts & recreation | 2013 |
| Infinity-Embroidery Ltd | Wholesale & retail | 2021 |
| Infosec Assist Ltd | Information & communication | 2020 |
| Infrabrick Ltd | Real estate | 2024 |
| Infrassistance Development Limited | Information & communication | 2011 |
| Infro Limited | Information & communication | 2025 |
| Infused Electrical Services Ltd | Construction | 2022 |
| Ingledale Centre Ltd | Real estate | 2005 |
| Ingram Lending Limited | Financial services | 2018 |
| Inheritance Tax Portal Limited | Professional & scientific | 2006 |
| Initial Stack Ltd | Information & communication | 2025 |
| Inktruzion Limited | Other services | 2012 |
| INNOV8 GB Ltd | Wholesale & retail | 2005 |
| Innovation Pro Ltd | Professional & scientific | 2013 |
| Inola Ltd | Information & communication | 2019 |
| Inovo Systems Limited | Manufacturing | 2014 |
| Insight Consultants Group Ltd | Other services | 2002 |
| Insight Solutions Consulting Group Limited | Professional & scientific | 2016 |
| Inspire Agencies Limited | Professional & scientific | 2018 |
| Inspire Mortgage Solutions Limited | Financial services | 2017 |
| Inspired Bygrace Limited | Information & communication | 2025 |
| Inspired Experiences Limited | Professional & scientific | 2008 |
| Inspired Security Systems Ltd | Information & communication | 2019 |
| Inspireperform Ltd | Professional & scientific | 2012 |
| Intech Controls Ltd | Manufacturing | 2013 |
| Integral Planning & Economics Limited | Professional & scientific | 2020 |
| Integrated Control Technology (Europe) Limited | Wholesale & retail | 2016 |
| Integrated Safety and Investigation Services LLP | | 2010 |
| Integrated Transport Consulting Limited | Professional & scientific | 2023 |
| Intelled Limited | Professional & scientific | 2024 |
| Intelli Labs Deutschland Ltd | Manufacturing | 2010 |
| Intelli Labs Ltd. | Manufacturing | 2008 |
| Intellicalx Consulting Services Limited | Professional & scientific | 2022 |