| International Projects Centre Limited | Education | 1998 |
| Interwoven Productions CIC | Arts & recreation | 2017 |
| Intramount Limited | Professional & scientific | 1998 |
| Intrepid Expeditions Ltd | Administrative & support | 2009 |
| Intrinsique Ltd | Education | 2009 |
| Intro Labs Ltd | Information & communication | 2023 |
| Introspective Psychotherapy Ltd | Other services | 2025 |
| Investegic Ltd | Real estate | 2022 |
| Investimo Limited | Real estate | 2021 |
| Investment Synergy Ltd | Professional & scientific | 2012 |
| Invoxa Ltd | Real estate | 2025 |
| Iola Music Ltd | Manufacturing | 2022 |
| Ionic Groundworks Ltd | Administrative & support | 2020 |
| Ionut Calinoiu Limited | Transport & logistics | 2021 |
| Iosub Dent Ltd | Health & social care | 2019 |
| Iph-Recruitment Ltd | Administrative & support | 2016 |
| IPM Fittings Ltd | Manufacturing | 2009 |
| Ipsa Consulting Limited | Other services | 2021 |
| IRD Medical & Surgical Ltd | Health & social care | 2009 |
| IRE 001 Limited | Energy | 2021 |
| Iridium Consulting Limited | Information & communication | 2002 |
| Ironclad Holdings Ltd | Real estate | 2024 |
| Ironclad Property Ltd | Real estate | 2024 |
| Ironclad Solutions Ltd | Construction | 2012 |
| Isansys Lifecare Limited | Manufacturing | 2010 |
| Isca Advisory Services Ltd | Professional & scientific | 2018 |
| Isca Archaeology Limited | Construction | 2020 |
| Isca Asset Management Ltd | Financial services | 2014 |
| Isca Bags Limited | Wholesale & retail | 2004 |
| Isca Biochemicals Limited | Manufacturing | 2011 |
| Isca Brands Limited | Professional & scientific | 2021 |
| Isca Care Support Limited | Administrative & support | 2023 |
| Isca Decorating Company Limited | Construction | 2010 |
| Isca Design Practice Ltd | Professional & scientific | 2022 |
| Isca Digital Limited | Other services | 2012 |
| Isca Digital Retail Ltd | Other services | 2019 |
| Isca Ecology Limited | Professional & scientific | 2025 |
| Isca Finance Ltd | Financial services | 2016 |
| Isca Fire and Safety Limited | Public administration | 2019 |
| Isca Fitness Limited | Arts & recreation | 2022 |
| Isca Group Holdings Ltd | Financial services | 2020 |
| Isca Heating & Plumbing Co. Ltd | Construction | 2001 |
| Isca Holdings Limited | Real estate | 2015 |
| Isca Housing Ltd | Households | 2019 |
| Isca Insight Ltd | Information & communication | 2025 |
| Isca Legal LLP | | 2013 |
| Isca Legal Solutions Limited | Professional & scientific | 2013 |
| Isca Maritime Security Services Ltd | Administrative & support | 2019 |
| Isca Operations Ltd | Real estate | 2026 |
| Isca Pest Control Limited | Other services | 2017 |
| Isca Recruitment Ltd | Administrative & support | 2015 |
| Isca Security Ltd | Administrative & support | 2026 |
| Isca Supported Living Limited | Health & social care | 2015 |
| Isca Ventures Limited | Professional & scientific | 2024 |
| Isca Wellbeing Ltd | Education | 2020 |
| Isca Windows & Property Services Limited | Construction | 2006 |
| Iscavia Holdings Limited | Professional & scientific | 2007 |
| Iscavia Limited | Transport & logistics | 1996 |
| Iscaware Ltd | Information & communication | 2022 |
| Ishelp.Co.Uk Limited | Information & communication | 2001 |
| Island (Cutter) Limited | Arts & recreation | 2006 |
| Islip Solar Park Limited | Energy | 2011 |
| Ismart Accessories Limited | Wholesale & retail | 2023 |
| Isservico Limited | Professional & scientific | 2025 |
| Istanbul Exeter Ltd | Hospitality | 2025 |
| Istdp Health Ltd | Health & social care | 2022 |
| Isteni Developments Limited | Financial services | 2019 |
| Isteni FRG Grosvenor BS2 Limited | Real estate | 2019 |
| Isteni Ltd | Real estate | 2017 |
| Isteni Property Holdings Limited | Real estate | 2018 |
| Istidam Consulting Ltd | Professional & scientific | 2022 |
| IT Champion Limited | Information & communication | 2009 |
| IT Systems Plus Limited | Professional & scientific | 1992 |
| ITC 001 Limited | Real estate | 2022 |
| ITC Investments Limited | Other services | 2020 |
| Ithaca Architecture Ltd | Information & communication | 2025 |
| Ithaca Property & Marketing Consultants Ltd | Professional & scientific | 2019 |
| ITS Disco Limited | Information & communication | 2023 |
| Itseeze Limited | Extraterritorial | 2008 |
| IVE Media Limited | Education | 2018 |
| IVY Aesthetics and Medical Consultancy Limited | Health & social care | 2023 |
| IVY Fish House Limited | Hospitality | 2020 |
| IXA Ltd | Information & communication | 2022 |
| IYA Group Ltd | Information & communication | 2025 |
| J & E Hewlett Ltd | Manufacturing | 2013 |
| J & G (Services) Limited | Information & communication | 2011 |
| J & L a Haimes Ltd. | Agriculture & fishing | 2013 |
| J & L Farming & Development Ltd | Hospitality | 2011 |
| J & NB Ltd | Professional & scientific | 2002 |
| J & P Turner (Building Contractors) Limited | Construction | 2000 |
| J & R Food Service Limited | Hospitality | 2003 |
| J & S Family Investments Limited | Real estate | 2022 |
| J a &C Properties Ltd | Real estate | 2024 |
| J a Cars (Exeter) Limited | Wholesale & retail | 2005 |
| J a Furzer Building Services Ltd | Construction | 2010 |
| J and a Camp Limited | Agriculture & fishing | 2022 |
| J and COE Properties Limited | Real estate | 2025 |
| J B Jones (Amusements) Limited | Real estate | 1955 |
| J Boston & Sons (Holdings) Limited | Construction | 2001 |
| J D S Agencies Ltd | Wholesale & retail | 2011 |