| ISV Homes Ltd | Real estate | 2025 |
| IT by Joker Ltd | Construction | 2018 |
| IT Consultancy Specialist Ltd | Information & communication | 2025 |
| IT Labsupport Ltd | Information & communication | 2020 |
| IT Networks Trade Ltd | Wholesale & retail | 2013 |
| IT Researches Ltd | Information & communication | 2020 |
| IT Solutions Services Ltd | Information & communication | 2019 |
| IT Surplus Ltd | Wholesale & retail | 2022 |
| It's a New Day CIC | Health & social care | 2024 |
| It's Fine Productions Ltd | Information & communication | 2023 |
| Ital Bangla Grocery Shop Ltd | Wholesale & retail | 2016 |
| Italian Food Supplies Limited | Wholesale & retail | 2020 |
| Italian Home Furnishings Ltd | Wholesale & retail | 2021 |
| Italian Roast Limited | Hospitality | 2013 |
| Italian Windows Cleaning Limited | Administrative & support | 2025 |
| Italk Limited | Professional & scientific | 2023 |
| Italyans Ltd | Hospitality | 2023 |
| Itanium Group Ltd | Information & communication | 2014 |
| Itar Dubai Ltd | Wholesale & retail | 2023 |
| Itara Consulting Limited | Information & communication | 2024 |
| Itasill Ltd | Wholesale & retail | 2023 |
| ITE Properties Limited | Real estate | 2022 |
| Itechppm Associates Ltd | Administrative & support | 2020 |
| Itechsoft Ltd | Information & communication | 2012 |
| Itee Cloud Ltd | Information & communication | 2018 |
| Itefaq Limited | Real estate | 2017 |
| Itera Ltd | Wholesale & retail | 2025 |
| Ites Rental Ltd | Administrative & support | 2020 |
| Ithubglobal Ltd | Wholesale & retail | 2024 |
| Itms Services Ltd | Information & communication | 2015 |
| ITQ Ltd | Information & communication | 2026 |
| Itquest Consultants (UK) Limited | Information & communication | 2004 |
| Itquest Limited | Information & communication | 2011 |
| ITR Services Limited | Professional & scientific | 2001 |
| ITS UR Builder Limited | Construction | 2022 |
| ITSERVICE24/7 Limited | Information & communication | 2014 |
| Itsolutioninbox Ltd | Information & communication | 2019 |
| Ittehad Consultants Ltd | Information & communication | 2022 |
| Itusnirav Limited | Administrative & support | 2025 |
| Itwa C.I.C. | Education | 2025 |
| Itzma Ltd | Information & communication | 2022 |
| Iuda.Uk Ltd | Construction | 2025 |
| IUH Invests Ltd | Real estate | 2024 |
| Iulian Postension Limited | Construction | 2018 |
| Iusco Carpenter Ltd | Construction | 2019 |
| Iusco Drylining Ltd | Construction | 2025 |
| Iusco Tiling Ltd | Manufacturing | 2018 |
| Iusi Stroy Limited | Construction | 2025 |
| IVA Chip Ltd | Manufacturing | 2022 |
| IVA EVE Ltd | Hospitality | 2021 |
| IVA Formwork Limited | Construction | 2016 |
| IVA Model Reports Ltd | Wholesale & retail | 2023 |
| Ivanthais Group Ltd | Construction | 2025 |
| Ivape Echo Ltd | Wholesale & retail | 2022 |
| Ivape Foxtrot Ltd | Wholesale & retail | 2022 |
| Ivape Golf Ltd | Wholesale & retail | 2024 |
| Ivape Hotel Ltd | Wholesale & retail | 2025 |
| Ivape Limehouse Ltd | Wholesale & retail | 2022 |
| Ivape London Ltd | Wholesale & retail | 2017 |
| Ivape Properties Ltd | Real estate | 2022 |
| Ivar IT Limited | Information & communication | 2017 |
| Ivaylo Foods Limited | Hospitality | 2024 |
| IVC Inovation Visual Construction Ltd | Construction | 2018 |
| Iveagh Avenue Limited | Real estate | 2023 |
| IVF London Ltd | Health & social care | 2016 |
| Ivoryspring Limited | | 1983 |
| IVS Brothers Ltd | Hospitality | 2022 |
| IVY Court Residents Company Limited | Households | 1973 |
| IVY Group Homes Ltd | Health & social care | 2024 |
| IVY Halls Pbsa Limited | Hospitality | 2025 |
| IVY League Property & Trading Ltd | Real estate | 2023 |
| IVY Rose Nails Ltd | Other services | 2025 |
| Ivydene Court Residents Association Limited | Households | 2014 |
| IW London Ltd | Administrative & support | 2025 |
| IW Shop Fittings UK Ltd | Construction | 2025 |
| Iwear Italia Limited | Wholesale & retail | 2014 |
| Ixtel Solutions Limited | Administrative & support | 2015 |
| IY & Idun LLP | | 2023 |
| IYI Foods Limited | Hospitality | 2025 |
| IZ Car Parts Ltd | Wholesale & retail | 2026 |
| IZ Store Ltd | Wholesale & retail | 2024 |
| Izear Security Group Ltd | Administrative & support | 2025 |
| Iziwa Ltd | Wholesale & retail | 2025 |
| Izizi Ltd | Wholesale & retail | 2025 |
| Izktraders Limited | Wholesale & retail | 2025 |
| IZM Labs Limited | Wholesale & retail | 2018 |
| Izuna Drop Ltd | Information & communication | 2024 |
| IZZ Properties Limited | Real estate | 2022 |
| Izzabela Logistics 17 Ltd | Transport & logistics | 2025 |
| Izzy Capital Ltd | Real estate | 2025 |
| Izzy East Ltd | Real estate | 2025 |
| Izzy Estates Ltd | Real estate | 2020 |
| Izzy Homes Ltd | Real estate | 2022 |
| Izzy Properties 1 Ltd | Real estate | 2025 |
| Izzy Properties Ltd | Real estate | 2023 |
| Izzy Property Solutions Ltd | Real estate | 2025 |
| Izzy Realty Solutions Ltd | Real estate | 2025 |
| Izzy Romford Ltd | Real estate | 2024 |
| J & a Investment Ltd | Real estate | 1998 |
| J & a Traders Ltd | Wholesale & retail | 2019 |