| Inter Sport Auto (UK) Limited | | 1982 |
| Interavon Limited | Real estate | 1976 |
| International Medical Technology Limited | Manufacturing | 1986 |
| Intoto Knowledge Ltd. | Professional & scientific | 2002 |
| Intuitionap Ltd | Education | 2025 |
| INV Group Ltd | Construction | 2023 |
| Invasive Plant Management Ltd | Water & waste | 2025 |
| Invest in Law Limited | Professional & scientific | 1972 |
| Investamove Ltd | Real estate | 2020 |
| Investart Ltd | Real estate | 2018 |
| Investments & Capital Limited | Financial services | 2026 |
| Invicto Limited | Extraterritorial | 2014 |
| Invisifilm Ltd | Wholesale & retail | 2015 |
| Invomag UK Ltd | Professional & scientific | 2023 |
| IOL Project Consultancy Limited | Professional & scientific | 2023 |
| IP Crime Directory Limited | Information & communication | 2020 |
| Ipa-Pharmacies Limited | Other services | 2002 |
| Iprovide Physio Limited | Administrative & support | 2014 |
| Iris Digital Health Consulting Ltd | Information & communication | 2022 |
| IRK Valley Property Holdings Limited | Construction | 2016 |
| Ironeye Group Ltd | Administrative & support | 2023 |
| Ironeye Recruitment Ltd | Administrative & support | 2017 |
| Ironhull Brokers Limited | Transport & logistics | 2026 |
| IRX Consultancy Ltd | Wholesale & retail | 2025 |
| ISH Locums Ltd | Health & social care | 2022 |
| Islamic Home Finance Ltd | Financial services | 2025 |
| Isonets Ltd | Information & communication | 2017 |
| Isra Healthcare Ltd | Health & social care | 2024 |
| IT IS ME Ltd | Information & communication | 2019 |
| ITB Consultancy Limited | Professional & scientific | 2022 |
| Itefaq Group Ltd | Construction | 2025 |
| Itefaq Himley Group Ltd | Real estate | 2026 |
| ITG Technologies Limited | Information & communication | 2005 |
| Itob Limited | Information & communication | 2000 |
| ITP Apollo Ltd | Real estate | 2025 |
| ITP Bury Ltd | Real estate | 2026 |
| Ittglobal Limited | Wholesale & retail | 2025 |
| IV Lions Limited | Financial services | 2012 |
| IVL Accountants Limited | Professional & scientific | 2022 |
| IVL Group Limited | Professional & scientific | 2018 |
| Ivorypharma Ltd | Wholesale & retail | 2024 |
| Ivytex Limited | Manufacturing | 1991 |
| IX Reach International Ltd | Information & communication | 2012 |
| IX Reach Ltd | Information & communication | 2004 |
| IXR Holdings Limited | Information & communication | 2012 |
| IXR Investments Ltd | Financial services | 2012 |
| Izml Investments Ltd | Financial services | 2019 |
| J & R Gutter Cleaning Plus Ltd | Administrative & support | 2025 |
| J & S Laws Ltd | Professional & scientific | 2020 |
| J & W Traders Ltd | Wholesale & retail | 2025 |
| J a Finnerty Limited | Construction | 2008 |
| J Admin Ltd | Wholesale & retail | 2025 |
| J C Quirk Limited | Extraterritorial | 2011 |
| J Gosling Services Ltd | Professional & scientific | 2017 |
| J H Accountancy Limited | Professional & scientific | 2012 |
| J J Ryan Ltd | Households | 2024 |
| J K Polymer Limited | Water & waste | 2010 |
| J L Naylor Property Development Limited | Real estate | 2021 |
| J Oldham Ltd | Professional & scientific | 2015 |
| J Suites Limited | Real estate | 2025 |
| J T H Associates Limited | Administrative & support | 2002 |
| J. Anderson Couriers Ltd | Transport & logistics | 2014 |
| J.A.P. Lighting Technology Ltd | Manufacturing | 2018 |
| J.C. Merchants Limited | Wholesale & retail | 1994 |
| J.T.Griffiths & Co Limited | Wholesale & retail | 2017 |
| J.U.K Ltd | Wholesale & retail | 2023 |
| J.W.M. Industrial Services Limited Ltd | Construction | 2002 |
| J3 Consulting and Pharmaceutical Services Ltd | Wholesale & retail | 2023 |
| Jaan Architects Ltd | Professional & scientific | 2018 |
| Jack Preston Barbering Ltd | Administrative & support | 2020 |
| Jack Wright Coaching Limited | Other services | 2025 |
| Jackson Quail Law Limited | Professional & scientific | 2021 |
| Jact Projects Ltd | Professional & scientific | 2024 |
| Jadiem Ltd | Professional & scientific | 2022 |
| Jaffrys Limited | Wholesale & retail | 2021 |
| JAG Aircraft Consultants Ltd | Manufacturing | 2019 |
| Jagdambay Properties Ltd | Real estate | 2025 |
| Jager Holdings Ltd | Financial services | 2024 |
| Jahstone Limited | Wholesale & retail | 2026 |
| JAI Yoga Ltd | Other services | 2024 |
| Jaindent Limited | Extraterritorial | 2013 |
| Jake Evans (Holding) Ltd | Financial services | 2026 |
| Jakesford Investments Limited | Professional & scientific | 2018 |
| Jals Properties Limited | Real estate | 2016 |
| JAM Pension Trustee Limited | Administrative & support | 2015 |
| JAM Recruitment Limited | Administrative & support | 2004 |
| James Galt & Co. Limited | Manufacturing | 1914 |
| James Gray Bespoke Ltd | Professional & scientific | 2021 |
| Jameson Acoustics Limited | Professional & scientific | 2022 |
| Jamm Properties Ltd | Households | 2018 |
| Janan Express Limited | Hospitality | 2025 |
| Jane Alexandra Hairdressing Cheadle Ltd | Other services | 2001 |
| Jane Bennison Associates Ltd | Professional & scientific | 2013 |
| Jane Mcdermott Coaching and Consultancy Ltd | Professional & scientific | 2020 |
| Janna Dining Ltd | Hospitality | 2023 |
| Janna Lebanese Restaurant Ltd | Hospitality | 2021 |
| Janus Business Solutions Limited | Information & communication | 2014 |
| Janus Collections Limited | Professional & scientific | 2015 |
| Janus Recoveries Limited | Professional & scientific | 2015 |
| Janus VC (UK) Limited | Financial services | 2018 |