| Inspired Glass and Stone Ltd | Manufacturing | 2025 |
| Inspired Homemakers Ltd | Real estate | 2021 |
| Inspired Mind Women’S Club (Imwc) Limited | Education | 2022 |
| Inspired to Lead Limited | Education | 2015 |
| Inspired Working Limited | Administrative & support | 2009 |
| INSPIRED2GETHER CIC | Health & social care | 2023 |
| Inspirit Entertainment Ltd | Information & communication | 2024 |
| Inspyred Ltd | Professional & scientific | 2019 |
| Insta UK Limited | Wholesale & retail | 2003 |
| Instacase Ltd | Manufacturing | 2008 |
| Instanuk Ltd | Professional & scientific | 2026 |
| Institute of Corporate Resilience (Iocr) Limited | Education | 2021 |
| Insurance First Brokers Ltd | Financial services | 1987 |
| Insure a Boat Limited | Extraterritorial | 2003 |
| Insuro Recruitment Limited | Administrative & support | 2026 |
| Integer Micro Systems Limited | Information & communication | 1989 |
| Integral Machines and Services Ltd | Manufacturing | 2018 |
| Integrated Handover Limited | Administrative & support | 2025 |
| Intelligent Building Services Limited | Construction | 2017 |
| Intelligent Mist Limited | Construction | 2013 |
| Intelligent Safeguarding Limited | Professional & scientific | 2026 |
| Intelligent Technology Limited | Manufacturing | 2025 |
| Intellirisk Limited | Information & communication | 2025 |
| Intelogistics LLP | | 2016 |
| Inter-Resolution Ltd | Administrative & support | 2022 |
| Interact Construction Solutions Limited | Construction | 2020 |
| Interesting Property Ltd | Real estate | 2024 |
| Interglobal Operations (UK) Limited | Administrative & support | 2015 |
| Interior Designs Wishlist Ltd | Wholesale & retail | 2024 |
| Interloper Limited | Professional & scientific | 2025 |
| Intermediation Ltd | Professional & scientific | 2025 |
| International Executive Solutions Limited | Administrative & support | 2007 |
| International Marine Purchasing Association | Information & communication | 2002 |
| International Video Products (Europe) Ltd. | Information & communication | 1990 |
| Intershape Limited | Wholesale & retail | 1998 |
| Intraflo Sensing Limited | Professional & scientific | 2024 |
| Intravena Limited | Extraterritorial | 2016 |
| Intrepid Owls Ltd | Information & communication | 2018 |
| Intrigue Homecare Ltd | Other services | 2016 |
| Intuitive Support Services Limited | Administrative & support | 2014 |
| Inva House Buyers Ltd | Real estate | 2023 |
| Inveena Ltd | Financial services | 2025 |
| Invent Design Studio Limited | Professional & scientific | 2017 |
| Inverstar Limited | Administrative & support | 2004 |
| Invest Development Ltd | Construction | 2018 |
| Investigating Countryside and Angling Research Projects CIC | Professional & scientific | 2018 |
| Investing From Adversity Limited | Real estate | 2014 |
| Invictus Barbers Ltd | Other services | 2018 |
| Invx Limited | Financial services | 2017 |
| Inwonderlandnails Colchester Ltd | Other services | 2025 |
| INZ Digital Art Ltd | Wholesale & retail | 2022 |
| ION Homes and Resort UK Limited | Real estate | 2025 |
| ION Student Living UK Limited | Real estate | 2025 |
| Iona Films Ltd | Professional & scientific | 2017 |
| Iphc Limited | Real estate | 2022 |
| Ipro Sport Distribution Ltd | Wholesale & retail | 2015 |
| Ipro Sport Holdings Limited | Wholesale & retail | 2015 |
| Ipro Sport International Limited | Wholesale & retail | 2016 |
| Ipro Sport Sponsorship Limited | Other services | 2016 |
| Iprojects (UK) Limited | Professional & scientific | 2007 |
| Ipsmort Limited | Extraterritorial | 2026 |
| Ipswich Developments Limited | Real estate | 2015 |
| Ipswich Medical Research Limited | Health & social care | 2008 |
| Ipswich Mortgages Limited | Financial services | 2020 |
| Ipswich PDP Sushi Ltd | Hospitality | 2023 |
| Ipswich Property Management Ltd | Construction | 2008 |
| Ipswich Road Management Company Limited | Households | 2006 |
| Ipswich Scuba Limited | Construction | 2023 |
| Ipswich Spine Clinic Limited | Extraterritorial | 2012 |
| Ipswich Waterfront Block Management Limited | Real estate | 2025 |
| IPW Financial Planning Ltd | Financial services | 2013 |
| IRB Property Ltd | Real estate | 2020 |
| Iris Fine Enamellers Ltd | Manufacturing | 2025 |
| Iris Performance Partners Limited | Professional & scientific | 2013 |
| Iron Brand Collective Ltd | Professional & scientific | 2024 |
| Iron Commerce Ltd | Wholesale & retail | 2024 |
| Iron Estates Limited | Real estate | 2020 |
| Ironborn Security Ltd | Administrative & support | 2021 |
| Irongate Labour Ltd | Administrative & support | 2026 |
| IRS Digital Ltd | Wholesale & retail | 2022 |
| Irvine Road Orchard Management Company Limited | Households | 2019 |
| Irwin Group (Holdings) Limited | Professional & scientific | 2013 |
| IS Enterprises International Limited | Wholesale & retail | 1998 |
| ISEC7 UK Limited | Information & communication | 2007 |
| ISG Advisory Services Ltd | Financial services | 2004 |
| Isg-It Limited | Information & communication | 2005 |
| Ishnar Property Services Ltd | Real estate | 2025 |
| Isington Track Services Ltd | Construction | 2022 |
| Isite Group Limited | Financial services | 2011 |
| Isite-Media Ltd | Information & communication | 2011 |
| Isitetv Limited | Administrative & support | 2006 |
| Island Advisors UK Ltd | Professional & scientific | 2019 |
| Island Air Limited | Transport & logistics | 2025 |
| Island ARB and Groundworks Ltd | Agriculture & fishing | 2014 |
| Island Dance Academy Ltd | Arts & recreation | 2024 |
| Island Environmental Consultants Limited | Professional & scientific | 2017 |
| Island Gelato Ltd | Extraterritorial | 2024 |
| Island Group Holdings Ltd | Financial services | 2022 |
| Island Hseq Ltd | Professional & scientific | 2019 |
| Island Inflatables Limited | Arts & recreation | 2023 |