| Iqa-Phills Ltd | Health & social care | 2025 |
| Iqbal Accounting Ltd | Financial services | 2025 |
| Iqbal Law Chambers Ltd | Administrative & support | 2010 |
| Iqony Renewables UK Ltd | Energy | 2018 |
| Iqrasjournal Ltd | Health & social care | 2023 |
| IR Group Holdings Limited | Financial services | 2018 |
| IR Group Investments Limited | Real estate | 2018 |
| IR Prop Ltd | Real estate | 2024 |
| Irabogie Cleaning Services Limited | Administrative & support | 2024 |
| Iradha Ltd | Administrative & support | 2023 |
| Irca Manufacturing UK Limited | Manufacturing | 2022 |
| Ireecare Limited | Health & social care | 2019 |
| IRF Trading Limited | Wholesale & retail | 2025 |
| Irina Moore Limited | Professional & scientific | 2006 |
| Iris Emissions Services Limited | Manufacturing | 2017 |
| Iris Homecare Ltd | Health & social care | 2025 |
| Iris Medical Aesthetics Ltd | Health & social care | 2026 |
| Irises Management Ltd | Real estate | 2024 |
| Irises Property Services Limited | Real estate | 2022 |
| Iron Events Ltd | Administrative & support | 2019 |
| Iron Trans Ltd | Transport & logistics | 2025 |
| Iron Worx Apparel Ltd | Wholesale & retail | 2025 |
| Ironbulk Ltd | Professional & scientific | 2026 |
| Ironforge Management Ltd | Real estate | 2025 |
| Ironing Plus Ltd | Other services | 2003 |
| Ironline Limited | Construction | 1988 |
| Irosaki Ltd | Information & communication | 2025 |
| Irpainting Ltd | Wholesale & retail | 2026 |
| Irrelon Property Limited | Real estate | 2018 |
| Irrelon Software Limited | Information & communication | 2011 |
| Irys Trans Ltd | Transport & logistics | 2015 |
| Iryscare Ltd | Health & social care | 2021 |
| IS Boutique Ltd | Wholesale & retail | 2026 |
| IS Cars Ltd | Wholesale & retail | 2010 |
| Isaac Properties Limited | Real estate | 2018 |
| Isaac Wholesale Limited | Wholesale & retail | 2005 |
| Isabelle Williams Limited | Administrative & support | 2019 |
| Isadeb Care Services Limited | Health & social care | 2025 |
| Isagrace Limited | Administrative & support | 2023 |
| Isar Residential Limited | Real estate | 2020 |
| ISB Consulting Limited | Professional & scientific | 2011 |
| Isithva Consultancy Services Ltd | Information & communication | 2024 |
| Islava Limited | Information & communication | 2013 |
| Ismail Investments Ltd | Construction | 2021 |
| Ismorix Ltd | Wholesale & retail | 2026 |
| Isolde Farms Ltd | Agriculture & fishing | 1997 |
| Ispas Trade Limited | Transport & logistics | 2023 |
| Istanbul Barber Peterborough Ltd | Other services | 2023 |
| Isupplies Group Limited | Wholesale & retail | 2023 |
| Isurus Fulfilment Limited | Other services | 2016 |
| Isuzus Import and Export Ltd | Wholesale & retail | 2024 |
| IT After Hours Ltd | Other services | 2014 |
| IT Appserv Ltd | Information & communication | 2012 |
| IT Big Bang Limited | Information & communication | 2016 |
| IT Infra Systems Limited | Information & communication | 2020 |
| IT Integrators Ltd | Information & communication | 2011 |
| IT Naturally Ltd. | Information & communication | 2019 |
| IT Product Supply Ltd | Wholesale & retail | 2023 |
| IT Testing Consultancy Limited | Administrative & support | 2015 |
| IT360 Pro Ltd | Information & communication | 2026 |
| Italian Prime Ltd | Hospitality | 2026 |
| Italian Street Food Ltd | Hospitality | 2026 |
| Itax Returns Ltd | Other services | 2012 |
| ITB42 Ltd | Administrative & support | 2013 |
| Itcinticity Ltd | Information & communication | 2014 |
| Itcon Limited | Information & communication | 2010 |
| Itec Web Services Ltd | Information & communication | 2023 |
| Itech Consulting Ltd | Information & communication | 2022 |
| ITM Systems Limited | Manufacturing | 2011 |
| ITO Couriers Ltd | Transport & logistics | 2017 |
| Itohan Logistics Ltd | Transport & logistics | 2020 |
| Ittap Limited | Information & communication | 2021 |
| Iusticon Services Ltd | Transport & logistics | 2018 |
| Ivan Noir Ltd | Wholesale & retail | 2023 |
| Ivaniak Limited | Wholesale & retail | 2025 |
| Ivatt Self Storage and Property Services Limited | Construction | 2014 |
| Ivatt Way (Management) Limited | Real estate | 1991 |
| Ives Estates Limited | Real estate | 2003 |
| Ives Ventures Limited | Hospitality | 2003 |
| IVF Construction Ltd | Construction | 2026 |
| Ivgt Group Ltd | Transport & logistics | 2023 |
| Ivory & Lace Group Ltd | Wholesale & retail | 2025 |
| Ivoryglowbeauty Ltd | Other services | 2026 |
| IVY & Friends Limited | Agriculture & fishing | 2025 |
| IVY Desserts Ltd | Hospitality | 2024 |
| IVY Thorndale Ltd | Real estate | 2018 |
| Ivybridge Residents Management Company Limited | Households | 2018 |
| Ivydale Restaurants Ltd | Hospitality | 2025 |
| IWF Consulting Limited | Construction | 2023 |
| Ix.Nineteen Ltd | Administrative & support | 2021 |
| Iyassen Limited | Health & social care | 2025 |
| IZ Care Ltd | Health & social care | 2018 |
| Izaans Ltd | Hospitality | 2018 |
| Izabela Walczak Ltd | Other services | 2018 |
| Izevolution Limited | Information & communication | 2023 |
| Izzet Haynes Developments Ltd | Real estate | 2023 |
| Izzet Haynes Group Ltd | Construction | 2017 |
| Izzo Hair Limited | Other services | 2025 |
| J & a Damarex Limited | Wholesale & retail | 2012 |
| J & a Woodroffe Farms Ltd | Agriculture & fishing | 2011 |