| IAN Brindle Consultancy Limited | Professional & scientific | 2024 |
| IAN Cooke Consulting Ltd | Professional & scientific | 2026 |
| IAN Falconer Marine Consultancy Limited | Professional & scientific | 2017 |
| IAN Leach Ltd | Construction | 2017 |
| IAN Learmonth. Strategic Solutions. Ltd | Administrative & support | 2014 |
| IAN Mcdermott Illustration Ltd | Professional & scientific | 2014 |
| IAN Monks Construction Services Ltd | Construction | 2008 |
| IAN Russell Consulting Ltd | Other services | 2020 |
| IAN Wigston Associates Limited | Professional & scientific | 2007 |
| IAS Unique Homes and Properties Limited | Real estate | 2024 |
| Ibidu Ventures Limited | Extraterritorial | 2024 |
| IC Automotive Consultancy Limited | Wholesale & retail | 2024 |
| ICC (Nineteen) Limited | Financial services | 1998 |
| Iceni Diagnostics Limited | Professional & scientific | 2021 |
| Iceni Glycoscience Limited | Professional & scientific | 2014 |
| Iceni Grill Ltd | Hospitality | 2019 |
| Iceni Law Limited | Professional & scientific | 2015 |
| Iceni Maintenance Limited | Administrative & support | 2007 |
| Iceni Marketing Ltd | Administrative & support | 2023 |
| Iceni Therapeutics Ltd | Professional & scientific | 2021 |
| Iceni Training Colchester Limited | Arts & recreation | 2015 |
| Icestar Media Limited | Information & communication | 2005 |
| ICK Healthcare Service Ltd | Administrative & support | 2018 |
| Icon Lifesaver Limited | Manufacturing | 2015 |
| Iconek Brands Ltd | Professional & scientific | 2023 |
| Icp-It Ltd | Professional & scientific | 2019 |
| ICT for Education Limited | Education | 2023 |
| Ictmagic Ltd | Education | 2025 |
| ID Bass Controls Limited | Real estate | 2017 |
| ID Plumbing Limited | Construction | 2015 |
| Idea Family Ltd | Financial services | 2024 |
| Ideachain Limited | Professional & scientific | 2013 |
| Ideal Carpentry Limited | Construction | 2015 |
| Ideal Chef Limited | Hospitality | 2013 |
| Ideal Construction Services Ltd | Construction | 2021 |
| Ideal Services Limited | Health & social care | 2019 |
| Ideal Temperature Limited | Extraterritorial | 2022 |
| IDEAS2DESIGN Limited | Information & communication | 2017 |
| Ideastobusiness Ltd | Information & communication | 2022 |
| Identity Fusion Limited | Wholesale & retail | 2020 |
| Idhairdressing Limited | Other services | 2018 |
| IDI PAC Ltd | Administrative & support | 2008 |
| Idmc Ltd | Construction | 2019 |
| IE Property Services Ltd | Administrative & support | 2021 |
| IEF Partners Limited | Administrative & support | 2022 |
| Iflex Clinic Ltd | Health & social care | 2019 |
| IFM Ltd | Other services | 2022 |
| Iftime Design Ltd | Other services | 2015 |
| IGA Global Ltd | Wholesale & retail | 2016 |
| Igbo Union Colchester CIC | Health & social care | 2025 |
| Igbo Union Essex and Suffolk CIC | Other services | 2024 |
| IGI Plumb & Heating Ltd | Construction | 2015 |
| Iglen Ltd | Real estate | 2016 |
| Ignite Digital Marketing Ltd | Information & communication | 2024 |
| Ignite Merchandise Solutions Ltd | Extraterritorial | 2018 |
| Igoranesti Ltd | Transport & logistics | 2026 |
| IH3 Limited | Professional & scientific | 2025 |
| Ihlb Ltd | Professional & scientific | 2025 |
| IIC Consulting Ltd | Public administration | 2012 |
| IJC Finance Ltd | Professional & scientific | 2019 |
| IK Accountancy Limited | Professional & scientific | 2017 |
| Ikan Health Limited | Health & social care | 2016 |
| Ikas Kitchens Limited | Wholesale & retail | 2009 |
| Ikem's Care Limited | Health & social care | 2021 |
| Ikon Mechanical Services Ltd | Construction | 2015 |
| Ikonik Designs Ltd | Manufacturing | 2011 |
| Ilana Primrose Ltd | Arts & recreation | 2020 |
| Ilecs-Fm Limited | Professional & scientific | 2005 |
| Illuminate Agency Ltd | Professional & scientific | 2014 |
| ILM Tuition Centre Ltd | Education | 2018 |
| IM Fire Security Ltd | Professional & scientific | 2024 |
| Image Key Limited | Construction | 2002 |
| Images Everything Limited | Arts & recreation | 2005 |
| Imaginateur Partners Ltd | Administrative & support | 2017 |
| Imagine Performing Arts Ltd | Education | 2023 |
| Imav Global Ltd | Professional & scientific | 2026 |
| Imdloz Limited | Professional & scientific | 2014 |
| IME Topco Limited | Financial services | 2023 |
| IMH Property Maintenance Ltd | Construction | 2025 |
| IML Servicing Limited | Construction | 2023 |
| Immadisetty Limited | Real estate | 2010 |
| Immadisetty Properties Limited | Real estate | 2020 |
| Imotec Electrical Ltd | Construction | 2021 |
| Impact Coatings Limited | Manufacturing | 2002 |
| Impact Entertainment Limited | Arts & recreation | 2012 |
| Impact Financial Limited | Professional & scientific | 2013 |
| Impact Global Group Limited | Other services | 2023 |
| Impact Lettings Ltd | Real estate | 2009 |
| Impact Medical Services Ltd | Administrative & support | 2003 |
| Impact Metalworks Ltd | Manufacturing | 2024 |
| Impact Sign Services Ltd | Professional & scientific | 2007 |
| Imperial Apartments Management Company Limited | Households | 2008 |
| Imperial Drylining Ltd | Construction | 2024 |
| Imperial Finishes Ltd | Construction | 2017 |
| Imperial Homes Group (Essex) Limited | Construction | 2020 |
| Imperial Strategy Global Ltd | Professional & scientific | 2026 |
| Imperium Echelon Ltd | Professional & scientific | 2025 |
| Implement Ascend AI Ltd | Information & communication | 2026 |
| Impression Technology Ltd | Information & communication | 2015 |
| Impressive Properties Ltd | Real estate | 2019 |