| Ignition Trustees Ltd. | Professional & scientific | 2023 |
| IKO Insulations UK Limited | Manufacturing | 2012 |
| Ilce Limited | Hospitality | 2024 |
| Illimitable AI Ltd | Information & communication | 2025 |
| Illumine Ltd | Financial services | 2022 |
| Ilsameda Tour Limited | Professional & scientific | 2024 |
| Imagine Chapter Ltd | Wholesale & retail | 2024 |
| Imax Car Keys Ltd | Manufacturing | 2021 |
| Immortal Tech Ltd | Administrative & support | 2019 |
| Impact Flooring (Cambs) Ltd | Construction | 2022 |
| Imperial Design (Kbso) Ltd | Wholesale & retail | 2020 |
| Imperial Pour Ltd | Hospitality | 2026 |
| Impie Ltd | Manufacturing | 2011 |
| IMR Aviation Safety Consulting Ltd | Professional & scientific | 2017 |
| IMS Precision Engineering Ltd. | Manufacturing | 1999 |
| IN Collaboration Limited | Administrative & support | 2022 |
| IN2EVENTS Ltd | Administrative & support | 2024 |
| Inangel Limited | Administrative & support | 2009 |
| Inclusive United Community Interest Company | Education | 2023 |
| Independent Seed Services Limited | Wholesale & retail | 1995 |
| Indian Palace Huntingdon Limited | Hospitality | 2024 |
| Indigo Cariad Ltd | Real estate | 2017 |
| Industrial Penstocks Limited | Manufacturing | 2022 |
| Industrial Valves Limited | Manufacturing | 2022 |
| Indy LAB Limited | Information & communication | 2021 |
| Ines Services Ltd | Other services | 2015 |
| Infinite Rise Limited | Professional & scientific | 2025 |
| Infinity Residence Ltd | Real estate | 2024 |
| Infinity Team World Ltd | Wholesale & retail | 2022 |
| Infitek Solutions Ltd | Information & communication | 2021 |
| Inflatebounce Limited | Arts & recreation | 2019 |
| Ingco Engineering Limited | Professional & scientific | 2023 |
| Initiate Limited | Professional & scientific | 2019 |
| Initiative Care UK Ltd | Health & social care | 2014 |
| Injenuity Limited | Information & communication | 2004 |
| Innovative Packaging Concepts Ltd | Administrative & support | 2018 |
| Insight Property Searches Limited | Information & communication | 2025 |
| Insignia Core Solutions Ltd | Information & communication | 2006 |
| Insignia Mats Limited | | 1985 |
| Inspire Property & Renovations Ltd | Construction | 2024 |
| Insure Risk Limited | Financial services | 2010 |
| Integra (ADB) Limited | Information & communication | 2016 |
| Integrity Edge Ltd | Professional & scientific | 2024 |
| Intelli Limited | Professional & scientific | 2025 |
| Intelligent Geographic Target Identification (Igti) Ltd | Mining & quarrying | 2025 |
| Intent Media Ltd | Information & communication | 2020 |
| Intentional Digital Ltd | Wholesale & retail | 2018 |
| Inter-Connect Plus Ltd | Professional & scientific | 2011 |
| Inter-Shipping Limited | Transport & logistics | 1995 |
| Interaction AHM Limited | Administrative & support | 2025 |
| Interaction Education Group Limited | Administrative & support | 2025 |
| Interaction Health & Social Care Limited | Administrative & support | 2023 |
| Interaction Lobster Limited | Administrative & support | 2025 |
| Interaction Recruitment PLC | Administrative & support | 1989 |
| Interaction Specialist Recruitment Limited | Administrative & support | 2015 |
| Interaction Staffing Solutions Limited | Administrative & support | 2008 |
| Interactive Financial Management Limited | Financial services | 2000 |
| Intermediate Contract Management Limited | Real estate | 2011 |
| International Education Connect Ltd | Education | 1989 |
| International Food Huntingdon Ltd | Wholesale & retail | 2023 |
| Interrelation Ltd | Professional & scientific | 2025 |
| Interveg Limited | Agriculture & fishing | 2000 |
| Investment Systems Ltd | Information & communication | 1988 |
| ION Therapeutics Limited | Professional & scientific | 2025 |
| Ipis Estates Ltd | Real estate | 2018 |
| Iqbals World Supermarket Ltd | Wholesale & retail | 2025 |
| IRB Advisory Limited | Professional & scientific | 2025 |
| Ireland Investment Group Ltd | Construction | 2021 |
| Irvine Cyto Consulting Ltd | Professional & scientific | 2018 |
| Irwin Building and Development (Holdings) Ltd | Financial services | 2009 |
| Irwin Building and Development Ltd | Construction | 1976 |
| Irwin Composites Ltd | Manufacturing | 2017 |
| Isaia Transport Ltd | Administrative & support | 2019 |
| ISC Software Solutions Limited | Information & communication | 2003 |
| Isgk Ltd | Transport & logistics | 2023 |
| Islanders Ibiza Ltd | Administrative & support | 2024 |
| Islands International Project Managers Ltd | Professional & scientific | 2023 |
| ISN Europe Limited | Wholesale & retail | 2002 |
| Isofast Limited | Wholesale & retail | 2007 |
| Italpresse UK Limited | Wholesale & retail | 2025 |
| Item Planet Ltd | Wholesale & retail | 2020 |
| Iterum Dynamics Ltd | Administrative & support | 2015 |
| Ivan Barrett Limited | Wholesale & retail | 2018 |
| Ivgundran Ltd | Public administration | 2025 |
| IVO Brewery Ltd | Manufacturing | 2019 |
| Izabella & Lukasz Ltd | Transport & logistics | 2018 |
| Izatrans Ltd | Transport & logistics | 2023 |
| J & a Carpets Ltd | Construction | 2015 |
| J & M Cliston Limited | Professional & scientific | 2020 |
| J & SA Consulting Ltd | Professional & scientific | 2017 |
| J & T Accounting Services Ltd | Professional & scientific | 2008 |
| J Brooks Ltd | Professional & scientific | 2025 |
| J D a Brickwork Ltd | Construction | 2023 |
| J Davis Trading Ltd | Hospitality | 2023 |
| J E Smith Holiday & Management Limited | Households | 2016 |
| J E Smith Sales Limited | Real estate | 2016 |
| J E Smith Trading Limited | Wholesale & retail | 2020 |
| J G Plumbing Services Limited | Construction | 2004 |
| J H Building Restoration Limited | Construction | 2013 |
| J H Corrugator Services Limited | Manufacturing | 2011 |