| Iseki UK & Ireland Limited | Wholesale & retail | 2017 |
| Ishfa Fashion Ltd | Wholesale & retail | 2025 |
| Islam & Psychophilosophy Ltd | Information & communication | 2026 |
| Island Pools (Holdings) Ltd | Administrative & support | 2019 |
| Island Properties G.B. Limited | Real estate | 1997 |
| Islandic Investments Ltd | Construction | 2014 |
| Isleink Limited | Real estate | 2024 |
| Isles & Storer Accountants LLP | | 2009 |
| Ismail Olanrewaju Oladapo Etti Limited | Extraterritorial | 2021 |
| Ismart Ltd | Wholesale & retail | 2016 |
| Isolutions London Ltd | Real estate | 2023 |
| Isolutions Property Services Ltd | Construction | 2021 |
| Isotek UK Limited | Financial services | 2023 |
| IT Brands Limited | Information & communication | 2011 |
| IT Planet MZ Ltd | Wholesale & retail | 2026 |
| IT Services at CAS Ltd | Information & communication | 2001 |
| ITA Group UK Limited | Information & communication | 1996 |
| Ital Collective Ltd | Professional & scientific | 2025 |
| Italian Sealife Chartering Limited | Transport & logistics | 2009 |
| Itembay Limited | Information & communication | 2019 |
| ITF Home Improvements Ltd | Construction | 2025 |
| ITF Home Ltd | Construction | 2025 |
| ITF Property Ltd | Real estate | 2017 |
| ITS ALL Savvy Limited | Information & communication | 2018 |
| ITS Systems Ltd. | Administrative & support | 2003 |
| Itutu Drive Limited | Transport & logistics | 2017 |
| Iulmar Ltd | Transport & logistics | 2023 |
| IV Restaurant Ltd | Hospitality | 2017 |
| IV Scaffolding Ltd | Construction | 2020 |
| Ivbs Drivers Ltd | Transport & logistics | 2018 |
| Ivedha UK Ltd | Information & communication | 2022 |
| Iveley Limited | Real estate | 1986 |
| Ivorypearl Limited | Wholesale & retail | 2025 |
| IVY Wellness Suffolk Ltd | Health & social care | 2024 |
| Iyaaz Limited | Hospitality | 2019 |
| Izakaya Suzuki Limited | Hospitality | 2025 |
| Izzy Property Limited | Real estate | 2012 |
| J & a Solutions Ltd | Wholesale & retail | 2005 |
| J & C (UK) Limited | Administrative & support | 2008 |
| J & C Cooper Properties Limited | Real estate | 2025 |
| J & C Surveying Services Ltd | Professional & scientific | 2015 |
| J & L Properties (Suffolk) Limited | Financial services | 2025 |
| J & P Contracts Limited | Construction | 2013 |
| J & S Logistics Ltd | Transport & logistics | 2018 |
| J & S Sahota Properties Ltd | Real estate | 2024 |
| J & T Nichols Plastering Ltd | Construction | 2012 |
| J and I Holdings 1517 Limited | Financial services | 2026 |
| J B Copy Limited | Professional & scientific | 2012 |
| J B S Commercial Consultants Ltd | Professional & scientific | 2015 |
| J B Turf & Landscapes Limited | Administrative & support | 2014 |
| J C Benn Ltd | Construction | 2018 |
| J Cloud Property Limited | Real estate | 2019 |
| J Cook Carpentry Limited | Manufacturing | 2022 |
| J D Lifting Limited | Professional & scientific | 2007 |
| J D Plumbing Contracts Limited | Other services | 2015 |
| J D Stock Master Thatcher Limited | Construction | 2021 |
| J Decosimo Limited | Wholesale & retail | 2006 |
| J Egan Limited | Hospitality | 2008 |
| J G Construction and Builders Limited | Construction | 2023 |
| J Hazelwood Window Cleaning Ltd | Administrative & support | 2023 |
| J Hudson Investments Ltd | Financial services | 2025 |
| J J Anders Bourne Property Management Ltd | Real estate | 2021 |
| J K K Solutions Limited | Information & communication | 2011 |
| J L Motorsport Limited | Arts & recreation | 2017 |
| J M Plumbing and Heating Services (East Anglia) Ltd | Construction | 2025 |
| J Mann Financial Ltd | Financial services | 2018 |
| J Meekings Floor Screeds Ltd | Construction | 2008 |
| J Melton Services Ltd | Information & communication | 2022 |
| J Olsen Clinical Consulting Ltd | Professional & scientific | 2025 |
| J P H Electrical (Eastern) Ltd | Construction | 2021 |
| J P H Storage Service (Ipswich) Ltd. | Real estate | 1996 |
| J P R Surveys Limited | Professional & scientific | 2013 |
| J P Siddle Properties Limited | Real estate | 2023 |
| J S Accounting Limited | Professional & scientific | 2002 |
| J S Global Cargo & Freight Disposal Limited | Water & waste | 2018 |
| J S Global Recycling Recruitment Limited | Administrative & support | 2019 |
| J Sheppard Properties Limited | Real estate | 2017 |
| J Studd Motors Limited | Administrative & support | 2013 |
| J Summers Financials Ltd | Professional & scientific | 2019 |
| J T Bolton Limited | Construction | 2016 |
| J T S Electrical Services Limited | Other services | 2017 |
| J V Neurology Ltd | Health & social care | 2025 |
| J W O'Dowd Ltd | Construction | 2015 |
| J W Osteopathy Limited | Health & social care | 2008 |
| J W S Shipping Limited | Transport & logistics | 2017 |
| J Will Limited | Construction | 2015 |
| J&G Properties (East Anglia) Ltd | Real estate | 2021 |
| J&J Auto Tech Ltd | Wholesale & retail | 2019 |
| J&J Foster Property Ltd | Real estate | 2019 |
| J&J Residential Services Limited | Real estate | 2018 |
| J&J Traders Ltd | Wholesale & retail | 2020 |
| J&L Living Ltd | Real estate | 2023 |
| J&L Properties Partnership Ltd | Real estate | 2024 |
| J&S Four Seasons Ltd | Construction | 2025 |
| J'S Wash on Wheels Ltd | Other services | 2017 |
| J. Cook (Tendring) Limited | Agriculture & fishing | 1959 |
| J. Montana Consultancy Limited | Transport & logistics | 2024 |
| J. Roberts (Holdings) Limited | Real estate | 1963 |
| J. Roberts (Property Investments) Limited | Financial services | 2016 |
| J. Swain Limited | Information & communication | 2024 |