| International Trimmings and Labels Limited | Manufacturing | 1989 |
| Interrupt Ltd | Professional & scientific | 2025 |
| Interstellar Groundworks Limited | Construction | 2023 |
| Interstellar Surfacing Limited | Construction | 2024 |
| Interview Angels Limited | Real estate | 2017 |
| Interweb Spark Limited | Information & communication | 1997 |
| Intexa Limited | Construction | 2016 |
| Intigo Limited | Information & communication | 2025 |
| Intoarb LLP | | 2024 |
| Intoku Fashion Ltd | Wholesale & retail | 2019 |
| Intra-Air Limited | Administrative & support | 2025 |
| Introrise Limited | Real estate | 1986 |
| Intu Veritas Limited | Professional & scientific | 2018 |
| Intulux Lighting Ltd | Wholesale & retail | 2015 |
| Investa Transport Ltd | Wholesale & retail | 2017 |
| Investcare 2000 Limited | Professional & scientific | 2001 |
| Investeq Group Ltd | Financial services | 2019 |
| Investigation and Examination Services Limited | Professional & scientific | 2023 |
| Investland Enterprise Limited | Real estate | 2023 |
| Investnest Property UK Ltd | Real estate | 2023 |
| Investormac Ltd | Real estate | 2022 |
| Investors Corporation Limited | Real estate | 2018 |
| Invictus 1980 Limited | Financial services | 2018 |
| Invictus 1985 Limited | Financial services | 2018 |
| Invictus Services Group Ltd | Energy | 2026 |
| Invictus Technology Group Ltd | Information & communication | 2020 |
| Invise Holdings Limited | Real estate | 2025 |
| Invise Limited | Professional & scientific | 2020 |
| Invisible Solutions Limited | Information & communication | 2005 |
| Invosis Limited | Information & communication | 2009 |
| Inwards Design LAB Ltd | Information & communication | 2026 |
| Inza Design Ltd | Construction | 2014 |
| Iogen Limited | Information & communication | 2001 |
| ION Water Products Ltd | Extraterritorial | 1992 |
| Ionescu Limited | Construction | 2008 |
| Ionsafe Ltd | Professional & scientific | 2024 |
| Ioprot VET Ltd | Professional & scientific | 2023 |
| IP 2023 Limited | Financial services | 2023 |
| IP House UK Holdings Ltd | Administrative & support | 2011 |
| IPG Rail Limited | Construction | 2011 |
| Iplace Financial Services Limited | Financial services | 2021 |
| Iplace Global Ltd | Professional & scientific | 2007 |
| IPR Tech Limited | Wholesale & retail | 2020 |
| Iproduce Direct Ltd | Wholesale & retail | 2019 |
| IQ Smart Solutions Limited | Information & communication | 2020 |
| Iqbal Sons Logistics Ltd | Transport & logistics | 2022 |
| Iqbals Investments Ltd | Financial services | 2023 |
| Ireckon Ltd | Wholesale & retail | 2023 |
| Iridium Transport Ltd | Transport & logistics | 2023 |
| Iris (Eco) Ltd | Agriculture & fishing | 2021 |
| Irita Marriott Auctioneers and Valuers Ltd | Wholesale & retail | 2023 |
| Irmc Sales & Marketing Limited | Professional & scientific | 2015 |
| Iron Gate Industries Ltd | Wholesale & retail | 2023 |
| Iron Gate Realty Limited | Real estate | 2006 |
| Iron Horse Legacy Ltd | Professional & scientific | 2026 |
| Iron Mason Ltd | Manufacturing | 2014 |
| Iron Oak Consultancy Ltd | Professional & scientific | 2024 |
| Iron World (Derby) Limited | Arts & recreation | 2019 |
| Ironforge Innovations Limited | Manufacturing | 1999 |
| Irongate Group Limited | Wholesale & retail | 2025 |
| Ironing Board (Derby) Limited | Other services | 2017 |
| IS Your Car Available Limited | Wholesale & retail | 2022 |
| ISA Clean Limited | Administrative & support | 2025 |
| Isaac.B. Limited | Hospitality | 2024 |
| Isaraa Limited | Wholesale & retail | 2021 |
| Isayy Investment Management Limited | Real estate | 2024 |
| Isayy Management Limited | Real estate | 2024 |
| ISH Barbers Ltd | Other services | 2026 |
| ISH Programme & Project Management Limited | Professional & scientific | 2018 |
| Isha Ltd | Transport & logistics | 2026 |
| Isha’S Treat and Groceries Ltd | Wholesale & retail | 2025 |
| Ishha Ltd | Wholesale & retail | 2024 |
| Ishvarankv Ltd | Real estate | 2018 |
| Isla Bear Balloons Ltd | Wholesale & retail | 2025 |
| Isla Property Limited | Professional & scientific | 2009 |
| ISM Auto Ltd | Wholesale & retail | 2022 |
| Isma WASIM786 Limited | Wholesale & retail | 2026 |
| Ismah Foods Limited | Wholesale & retail | 2020 |
| Ismail Care Limited | Health & social care | 2023 |
| Ismsafetysolutions Limited | Professional & scientific | 2024 |
| Isoblue Limited | Administrative & support | 2000 |
| Isoquant Ltd | Real estate | 2012 |
| Istanbul Restaurant Limited | Hospitality | 2023 |
| Istanbul Shawarma Grill Ltd | Hospitality | 2024 |
| IT Baron Ltd | Information & communication | 2017 |
| IT Collections Ltd | Information & communication | 2007 |
| IT Derby Ltd | Wholesale & retail | 2013 |
| IT Fusion Hub Ltd | Information & communication | 2024 |
| IT Project Management Solutions Ltd | Information & communication | 2017 |
| IT Projects Delivery Ltd. | Professional & scientific | 2013 |
| IT Properties Limited | Real estate | 2019 |
| IT Solutions & Support Limited | Information & communication | 2013 |
| IT Studios Ltd | Other services | 2025 |
| IT Works Organics Limited | Manufacturing | 2026 |
| It's Time to Talk Ltd. | Health & social care | 2015 |
| Italian Cucina Ltd | Hospitality | 2022 |
| Italigu Limited | Construction | 2022 |
| ITB Fabrications Limited | Manufacturing | 2018 |
| Itchamps Software Private Limited | Information & communication | 2023 |
| Ithaka Estates Limited | Real estate | 2022 |