| Integral Construction Solutions Ltd | Construction | 2026 |
| Intense Group UK Ltd | Information & communication | 2023 |
| Interaf Group Ltd | Wholesale & retail | 2023 |
| Intercon Site Supplies and Services Ltd | Wholesale & retail | 2021 |
| Interface Plus Ltd | Wholesale & retail | 2023 |
| Interfresh Limited | Extraterritorial | 2013 |
| Interica Limited | Information & communication | 2004 |
| International Distribution & Transport Limited | Transport & logistics | 2005 |
| Internet Media Services Limited | Information & communication | 2004 |
| Intime Services Limited | Professional & scientific | 2016 |
| Intrados Construction Limited | Construction | 2018 |
| Intu Technology Ltd | Information & communication | 2023 |
| Inusitato Favore Limited | Administrative & support | 2022 |
| Inveco Ltd | Information & communication | 2024 |
| Inventica Investments Ltd | Real estate | 2010 |
| Inventive Developments Ltd | Real estate | 2025 |
| Inventive Sales Ltd | Other services | 2021 |
| Invest (Bean) Ltd | Real estate | 2010 |
| Investrive Dwellings Limited | Real estate | 2024 |
| Invicta Events Ltd | Arts & recreation | 2025 |
| Invicta Financial Consulting Limited | Professional & scientific | 2021 |
| Invicta Marine Limited | Manufacturing | 2007 |
| Invicta Resin and Paving Limited | Construction | 2024 |
| Invicta Workshops Limited | Real estate | 1996 |
| Invictus Global Logistics Ltd | Transport & logistics | 2018 |
| IOI Risk Engineering Limited | Professional & scientific | 2020 |
| ION Z Ltd | Construction | 2017 |
| Ionistrans Ltd | Transport & logistics | 2025 |
| Ipcm Ltd | Hospitality | 2024 |
| IPM Building Ltd | Construction | 2020 |
| IQ Awards Limited | Education | 2022 |
| IQ Gadgets Limited | Wholesale & retail | 2019 |
| Iracc Ltd | Construction | 2020 |
| Iraj Properties Ltd | Real estate | 2024 |
| IRI IRI Ltd | Manufacturing | 2022 |
| Iris Estates Limited | Real estate | 1960 |
| Irish Commercial Funding Ltd | Financial services | 2023 |
| Iron Mill Residents Association Limited | Real estate | 1986 |
| Ironstone Logistics Ltd | Transport & logistics | 2025 |
| IS Build Group Ltd | Other services | 2024 |
| IS Expert Ltd | Transport & logistics | 2015 |
| Isabelle Austin Ltd | Professional & scientific | 2021 |
| Isam Services Ltd | Transport & logistics | 2026 |
| Isano Connect Ltd | Administrative & support | 2013 |
| Isanti Ltd | Professional & scientific | 2015 |
| Isas Developments Ltd | Real estate | 2020 |
| ISG Facilities Management Ltd | Administrative & support | 2025 |
| ISG Specialist Services Ltd | Administrative & support | 2025 |
| Ishola Property Management Ltd | Real estate | 2020 |
| ISL Legals Ltd | Professional & scientific | 2015 |
| Island Property Maintenance Ltd | Real estate | 2014 |
| ISOCO4 Limited | Professional & scientific | 2017 |
| ISOCO5 Limited | Other services | 2008 |
| Isoken Ltd | Health & social care | 2020 |
| Isrkicks Ltd | Professional & scientific | 2022 |
| Istanbulmrkt Ltd | Wholesale & retail | 2025 |
| IT Merge Ltd | Information & communication | 2012 |
| IT Setup Ltd. | Professional & scientific | 2012 |
| IT Web Services Limited | Information & communication | 2012 |
| Italian Building Centre Ltd | Real estate | 2020 |
| Itech Projects Ltd | Information & communication | 2017 |
| ITERATION5 Limited | Information & communication | 2020 |
| Itgenius Ltd | Information & communication | 2023 |
| Itradent Limited | Real estate | 2005 |
| IVY Winn Interiors Ltd | Manufacturing | 2019 |
| IW & Co Consulting Ltd | Professional & scientific | 2025 |
| Iwade Developments (Kent) Limited | Construction | 2022 |
| Iwis Holdings Limited | Real estate | 2022 |
| Iwonfitness Limited | Other services | 2024 |
| Iworld Inc Global Solutions Ltd | Professional & scientific | 2026 |
| Iyle Ltd | Information & communication | 2012 |
| Izabela 2020 Ltd | Construction | 2023 |
| Izmo Ltd | Professional & scientific | 2020 |
| J & B Martin (Crayford & Fawkham) Limited | Agriculture & fishing | 1913 |
| J & B Martin (Holdings) Limited | Financial services | 2014 |
| J & B UK Sales Ltd | Wholesale & retail | 2023 |
| J & E Hall Limited | Manufacturing | 1995 |
| J & F Quantity Surveying Services Ltd | Construction | 2023 |
| J & H Haulage Limited | Transport & logistics | 2006 |
| J & M Construction (Kent) Limited | Construction | 2009 |
| J & O Building and Maintenance Services Ltd | Administrative & support | 2023 |
| J & S Brickwork Limited | Construction | 2004 |
| J & S Golding Ltd | Financial services | 2020 |
| J Abrahams Electrical Limited | Construction | 2025 |
| J Bate Investments Limited | Real estate | 2020 |
| J Clubb Developments Limited | Financial services | 2017 |
| J Clubb Holdings Limited | Professional & scientific | 2003 |
| J D Ductwork Solutions Limited | Construction | 2018 |
| J Davies Contracting Limited | Construction | 2014 |
| J Dickins Property Ltd | Construction | 2023 |
| J F Scaffolding Ltd | Construction | 2014 |
| J H Elevators Limited | Construction | 1999 |
| J H Elevators Management Services Ltd | Administrative & support | 2024 |
| J H G London Ltd | Construction | 2025 |
| J H Group (London) Ltd | Financial services | 2023 |
| J H Plastering Services Ltd. | Construction | 2007 |
| J H&S Group Ltd | Real estate | 2026 |
| J I L Property Investment Limited | Real estate | 2017 |
| J J Norcross Ltd | Wholesale & retail | 2006 |
| J L Decorators S.E. Ltd | Construction | 2019 |