| Investment Business Property Ltd | Financial services | 2026 |
| Investordeck Horizon Ltd | Professional & scientific | 2014 |
| Invicta Building Services Limited | Construction | 2003 |
| Inview Africa Limited | Information & communication | 2015 |
| IO Investments Ltd | Real estate | 2023 |
| ION Fit Ltd | Wholesale & retail | 2026 |
| ION VT Limited | Real estate | 2025 |
| Iona Civil Engineers Limited | Construction | 2018 |
| Ionic Development Consultancy Limited | Professional & scientific | 2006 |
| Ioypco Ltd | Information & communication | 2025 |
| IP Homes Ltd | Real estate | 2020 |
| IPM Corporation Ltd | Professional & scientific | 2025 |
| Ipro Sport (Nigeria) Limited | Wholesale & retail | 2021 |
| IPS Bridge 2 Limited | Construction | 2023 |
| IPS Bridge Limited | Real estate | 2020 |
| IPS Developments 2 Limited | Real estate | 2021 |
| IPS Developments Limited | Real estate | 2020 |
| IPS Lease Limited | Real estate | 2020 |
| IPS Propinvest Limited | Real estate | 2020 |
| IPS Purley Limited | Real estate | 2021 |
| IPS Rent Limited | Real estate | 2020 |
| Iqdn Limited | Information & communication | 2017 |
| IRC (MM) Ltd | Administrative & support | 2008 |
| Iris Complete Solutions Ltd | Construction | 2026 |
| Iris Therapies Ltd | Health & social care | 2016 |
| IRO Sushi Salisbury Ltd | Hospitality | 2026 |
| Iron Athlete Ltd | Wholesale & retail | 2025 |
| Iron Sharpens Iron Foundation CIC | Health & social care | 2025 |
| Is.G Metalworks Limited | Manufacturing | 2021 |
| Isaac Baah Ltd | Wholesale & retail | 2026 |
| Isaac Daniel Limited | Real estate | 2024 |
| Isafoods Trading Limited | Wholesale & retail | 2021 |
| ISC Logistics Ltd | Transport & logistics | 2020 |
| ISG Education Assist CIC | Education | 2025 |
| Isha Enterprises Ltd | Wholesale & retail | 2026 |
| Island Flames Limited | Construction | 2012 |
| Islington Leaseholders Association Ltd | Other services | 2010 |
| Ismael Security Limited | Extraterritorial | 2021 |
| Isocan Limited | Hospitality | 2024 |
| It's a Lovelace Thing & Co Limited | Wholesale & retail | 2023 |
| ITA Solutions Limited | Professional & scientific | 2012 |
| Italico Renovation Ltd | Construction | 2021 |
| Itpp Europe Ltd | Information & communication | 2020 |
| Itrom UK | | 2002 |
| Ivan Cudby Sculptor Ltd | Manufacturing | 2025 |
| Ivan Nenov Design Studio Limited | Other services | 2023 |
| Ivconsulto Ltd | Professional & scientific | 2026 |
| Iverbalize Limited | Professional & scientific | 2017 |
| IVY Legal Limited | Professional & scientific | 2013 |
| IVY8 Ltd | Hospitality | 2023 |
| Ivydene Lodge (Shirley) RTM Company Limited | Households | 2012 |
| IWV Holdings Ltd | Real estate | 2021 |
| Izgu Consulting Limited | Professional & scientific | 2019 |
| IZM Systems Ltd | Information & communication | 2023 |
| J Wilson SFX Ltd | Administrative & support | 2017 |
| J & F Goldfire Limited | Construction | 2006 |
| J & H Fire Protection (UK) Limited | Other services | 2001 |
| J & R Domestic and Commercial Renovation Ltd | Construction | 2026 |
| J & R Partnership Ltd | Wholesale & retail | 2022 |
| J & T Consulting Services Limited | Professional & scientific | 2017 |
| J a T Electrical Services LLP | | 2009 |
| J Belle Beauty Limited | Other services | 2020 |
| J Biggs Limited | Arts & recreation | 2005 |
| J Cotter Limited | Energy | 2015 |
| J Coveney Ltd | Administrative & support | 2020 |
| J Coveney Properties Ltd | Real estate | 2026 |
| J Ffrench Limited | Construction | 2001 |
| J Marlow Ltd | Professional & scientific | 2019 |
| J P Interiors Limited | Construction | 2007 |
| J R Slee Building and Joinery Contractors Limited | Construction | 2002 |
| J S Bespoke Limited | Construction | 2019 |
| J S Moves Limited | Other services | 2014 |
| J Spencer Properties Limited | Real estate | 2020 |
| J W Contract Services Limited | Construction | 1999 |
| J W Mcdonald Building Services Limited | Construction | 2006 |
| J W Mcdonald Property Services Limited | Construction | 2013 |
| J&D Flourish Limited | Health & social care | 2018 |
| J&M Media Limited | Information & communication | 2014 |
| J&T Goods Ltd | Wholesale & retail | 2023 |
| J&V Plastering Limited | Construction | 2020 |
| J.Coopers Plumbing & Heating Ltd | Construction | 2025 |
| J.E.C Electrical Contractors Ltd | Construction | 2018 |
| J.Irwin Davis Limited | Financial services | 1934 |
| J.M.Collins Investments Limited | Real estate | 2021 |
| J.Mcauley Ltd | Administrative & support | 2010 |
| J.Pop&Son Limited | Construction | 2020 |
| J.V. Tomlin Limited | Health & social care | 2014 |
| J.W.Atkinson Limited | Professional & scientific | 2003 |
| J3-LEMSEB UK Ltd | Wholesale & retail | 2024 |
| JA Lofts Ltd | Construction | 2016 |
| JA Squared Accountants Limited | Professional & scientific | 2026 |
| Ja.Wastemanagementservices Ltd | Water & waste | 2026 |
| Jaad Consult Limited | Professional & scientific | 2021 |
| Jabenian Limited | Information & communication | 2011 |
| JAC Commercial Services Limited | Professional & scientific | 2018 |
| Jacek Skorczynski Limited | Administrative & support | 2013 |
| Jacek&Monika Property Services Ltd | Construction | 2025 |
| Jack Hadlum Ltd | Professional & scientific | 2019 |
| Jack Louis Ltd | Professional & scientific | 2023 |
| Jack's Barbers Ltd | Other services | 2016 |