| Intra Mare Limited | Administrative & support | 2008 |
| Intrepid Bakers (Tufnell Park) Ltd | Hospitality | 2022 |
| Intro Crowd Ltd | Financial services | 2015 |
| INV Technologies Ltd | Information & communication | 2014 |
| Inventory 4 Let’S.Com Limited | Information & communication | 2015 |
| Inverness International Limited | Administrative & support | 2016 |
| Invest Renovations Ltd | Construction | 2024 |
| Investigations Direct Limited | Administrative & support | 2010 |
| Invoice Solution Ltd | Professional & scientific | 2016 |
| Ioannou Property Group Limited | Administrative & support | 2017 |
| Iona Investments Limited | Real estate | 2021 |
| Ionic Property Developments Limited | Construction | 2021 |
| Ioptima Investments Limited | Financial services | 2021 |
| Ioptima Software Consultancy Limited | Information & communication | 2012 |
| Iosif Construction Ltd | Construction | 2022 |
| IOT3 Ltd | Professional & scientific | 2018 |
| IPE Ventures Limited | Financial services | 2017 |
| Iprop Ltd | Real estate | 2020 |
| IPS Joinery Limited | Construction | 2014 |
| Iran Table Ltd | Hospitality | 2025 |
| Iraqi Company for Financing Smes Ltd | Financial services | 2025 |
| Iraya UK Ltd | Other services | 2018 |
| Irayne One Limited | Other services | 2023 |
| Irayne Three Limited | Other services | 2023 |
| Irayne Two Limited | Other services | 2023 |
| Irinel Security Ltd | Administrative & support | 2021 |
| Irmaco Security Ltd | Administrative & support | 2023 |
| Irobiclose Limited | Transport & logistics | 2025 |
| Iroko Medical Consulting Limited | Health & social care | 2023 |
| Ironfort Group Limited | Information & communication | 2026 |
| Ironrock Management Ltd | Professional & scientific | 2023 |
| Ironside Security Ltd | Administrative & support | 2022 |
| Irv-Cater Limited | Hospitality | 2017 |
| Isaac's Housing Ltd | Real estate | 2021 |
| Isabella's Stays Limited | Real estate | 2026 |
| ISB Property Ltd | Administrative & support | 2017 |
| Isdntovoip Limited | Information & communication | 2010 |
| ISE View Consulting Limited | Professional & scientific | 2025 |
| Isel Construction Ltd | Construction | 2018 |
| Iseven Autos Ltd | Transport & logistics | 2025 |
| Ishvari Holdings Ltd | Real estate | 2026 |
| Isky Ltd | Professional & scientific | 2018 |
| Island Creek Limited | Information & communication | 2011 |
| Isovistainsulation Ltd | Construction | 2017 |
| Ispirato Limited | Wholesale & retail | 1971 |
| ISR 92 Ltd | Transport & logistics | 2017 |
| Issam 2 Ltd | Real estate | 2020 |
| Issam Ltd | Administrative & support | 2020 |
| Istanblu Limited | Hospitality | 2019 |
| IT Digital Limited | Administrative & support | 2016 |
| IT in Cloud Limited | Information & communication | 2015 |
| It-Techconsultancy Ltd | Information & communication | 2018 |
| Italia Conti Holdings Limited | Professional & scientific | 1980 |
| Itech Data Analytics Ltd | Administrative & support | 2017 |
| Itech-Media Ltd | Information & communication | 2010 |
| Ithinkhome Inc Limited | Wholesale & retail | 2025 |
| Itomas Design Ltd | Professional & scientific | 2002 |
| ITQ Image Through Quality Limited | Administrative & support | 2011 |
| ITS Interactive POS Ltd | Manufacturing | 2015 |
| IVA London Limited | Hospitality | 2024 |
| IVA Properties Ltd | Real estate | 2026 |
| Ivan's Carpentry Ltd | Manufacturing | 2017 |
| IWI Limited | Information & communication | 2002 |
| IZ Crystal Limited | Wholesale & retail | 2025 |
| Izmir Food Limited | Hospitality | 2017 |
| IZR35 Ltd | Wholesale & retail | 2020 |
| J & C Food Promotions Ltd | Hospitality | 2018 |
| J & J Asphalt Ltd | Construction | 2007 |
| J & L Build Limited | Construction | 2002 |
| J & L Hunsdon Limited | Construction | 2017 |
| J & M Product Sales Ltd | Wholesale & retail | 2026 |
| J & WJ Morris Limited | Transport & logistics | 2015 |
| J a Heating & Plumbing Limited | Construction | 2011 |
| J and M Haulage Limited | Transport & logistics | 2003 |
| J and S the Langley RAJ Limited | Hospitality | 2018 |
| J B Hill Trading Limited | Administrative & support | 2007 |
| J Charles Property Services Limited | Real estate | 2015 |
| J Cole Properties Ltd | Real estate | 2024 |
| J Cook Ltd | Construction | 2018 |
| J Dhanda Limited | Professional & scientific | 2014 |
| J E B Farriery Services Ltd | Agriculture & fishing | 2016 |
| J Hollins Health Ltd | Health & social care | 2009 |
| J J a Coachworks Limited | Administrative & support | 2013 |
| J Johnstone Carpentry & Joinery Limited | Construction | 2025 |
| J L M Electrical Contracting Limited | Construction | 2012 |
| J L W Recruitment Design Ltd | Professional & scientific | 2012 |
| J M W Property Services Limited | Real estate | 2002 |
| J Newman Investments Ltd | Real estate | 2025 |
| J P Neapolitan Pizza Ltd | Hospitality | 2026 |
| J P R Recycling Limited | Water & waste | 2002 |
| J Pach Limited | Health & social care | 2023 |
| J R E W Architecture Ltd | Professional & scientific | 2024 |
| J Tech Roofing Ltd | Construction | 2013 |
| J Waller Law Limited | Professional & scientific | 2020 |
| J ZEX Holdings Ltd | Real estate | 2022 |
| J&Ds Investments Ltd | Real estate | 2019 |
| J-Stars Coaching Ltd | Arts & recreation | 2014 |
| J. Andy London Ltd | Manufacturing | 2026 |
| J.C. Watson Holdings Limited | Other services | 2015 |
| J.C. Watson Mechanical Limited | Other services | 2015 |