| IAM Public Relations Limited | Professional & scientific | 2021 |
| IAM Technology Group Limited | Information & communication | 2016 |
| Iamp Management Company Limited | Real estate | 2018 |
| Iamsamira Ltd | Information & communication | 2024 |
| IAN Barton Ltd | Administrative & support | 2018 |
| IAN Coxan Consultancy Ltd | Professional & scientific | 2021 |
| IAN Heald Limited | Real estate | 2013 |
| IAN K Orford Limited | Manufacturing | 2025 |
| IAN Scott (Sheffield) Limited | Hospitality | 2007 |
| IAN Spencer and Associates Limited | Professional & scientific | 2009 |
| IAN Stacey Consultancy Limited | Real estate | 2013 |
| IAN Truelove (Optometrist) Limited | Wholesale & retail | 2002 |
| IAN Walsh Consultancy Limited | Professional & scientific | 2019 |
| IAN Whitehead Contract Furnishing Limited | Manufacturing | 1993 |
| Ianura Ltd | Manufacturing | 2025 |
| Iarlaith NI Fheorais Limited | Arts & recreation | 2022 |
| Iatro Partners Ltd | Information & communication | 2019 |
| IAV Holdings Limited | Arts & recreation | 2025 |
| IB B2C Ltd | Transport & logistics | 2018 |
| IB Construction Services Ltd | Wholesale & retail | 2007 |
| IBA Data Limited | Administrative & support | 2014 |
| IBA Molecular UK Limited | Administrative & support | 2003 |
| Ibberson Ventures Limited | Hospitality | 2026 |
| Ibbertya Holdings Limited | Construction | 2023 |
| Ibbotson Plumbing Limited | Construction | 2024 |
| IBC - Inco Building Contractors Limited | Construction | 2006 |
| IBC Tanks UK Ltd | Wholesale & retail | 2024 |
| Iberico Ltd | Hospitality | 2020 |
| Ibex Automation Ltd | Information & communication | 2016 |
| Ibex Facades Ltd | Construction | 2023 |
| Ibex Touring Limited | Administrative & support | 2018 |
| IBK Initiatives Ltd | Health & social care | 2005 |
| IBL Projects Ltd | Construction | 2022 |
| IBN Battuta International Ltd | Professional & scientific | 2026 |
| IBN Building & Joinery Limited | Construction | 2008 |
| Ibnjarirtours Ltd | Administrative & support | 2026 |
| Ibokeh Ltd | Professional & scientific | 2022 |
| Ibraheem Ijaz Limited | Health & social care | 2023 |
| Ibrahim Capital Ltd | Real estate | 2021 |
| Ibrahim Taxi Services Ltd | Transport & logistics | 2026 |
| Ibrahimi Health Ltd | Health & social care | 2012 |
| Ibrahimis Ltd. | Hospitality | 2021 |
| Ibrahims Halal Meat and Grocery Ltd | Wholesale & retail | 2019 |
| Ibrar Groups Ltd | Real estate | 2023 |
| Ibridge Programme Management Limited | Professional & scientific | 2004 |
| Ibtb Ltd | Wholesale & retail | 2025 |
| IC 107 Limited | Professional & scientific | 2015 |
| ICA Corporate Limited | Administrative & support | 2024 |
| ICA Group Ltd | Financial services | 2019 |
| ICA Investment Limited | Administrative & support | 2024 |
| ICA Limited | Administrative & support | 2024 |
| ICA Support Limited | Administrative & support | 2024 |
| Icabbi UK Ltd | Information & communication | 2015 |
| Icableuk Ltd | Information & communication | 2011 |
| ICD Applied Technologies Ltd | Professional & scientific | 2020 |
| ICD Europe Ltd. | Wholesale & retail | 2016 |
| Ice Grape Food Ltd | Wholesale & retail | 2024 |
| Ice Hockey UK Limited | Arts & recreation | 1999 |
| Ice HUT Creamery Ltd | Hospitality | 2017 |
| Ice Pops UK Ltd | Manufacturing | 2021 |
| Ice Station Zebra Holdings Limited | Financial services | 2025 |
| Iceburg Attitude Limited | Wholesale & retail | 2022 |
| Icelandair Holidays Ltd | Administrative & support | 1991 |
| Icestar Ltd | Manufacturing | 2012 |
| Icila Limited | Professional & scientific | 2015 |
| Ickle People Limited | Wholesale & retail | 2011 |
| Ickles Cottage Trust Limited | Real estate | 1936 |
| Icladd Limited | Wholesale & retail | 2016 |
| Iclark Consultancy Ltd | Information & communication | 2021 |
| Icmea-Uk Ltd | Manufacturing | 2018 |
| Icompare Building Products Limited | Administrative & support | 2013 |
| Icompliance Ltd | Information & communication | 2021 |
| Iconic Inspection Connection Ltd | Professional & scientific | 2012 |
| Iconnect Phones Limited | Wholesale & retail | 2024 |
| Iconnect Solutions Ltd | Information & communication | 2019 |
| Icpav Limited | Administrative & support | 2020 |
| Icraft Interiors Ltd | Wholesale & retail | 2025 |
| ICS Facility Services Limited | Other services | 2005 |
| ICT & Data Services Group Limited | Information & communication | 2011 |
| ICT Professionals Ltd. | Information & communication | 2003 |
| Icyartco Ltd | Wholesale & retail | 2024 |
| ID Properties Services Limited | Real estate | 2025 |
| ID Window Blinds Ltd | Manufacturing | 2014 |
| Id-Squared Limited | Health & social care | 2022 |
| IDA MAE Ltd | Information & communication | 2018 |
| Idakk Ltd | Public administration | 2022 |
| Idaq Limited | Information & communication | 2003 |
| Idav Logistics Limited | Administrative & support | 2024 |
| IDB Developments Ltd | Construction | 2023 |
| IDB Experts Ltd | Professional & scientific | 2024 |
| IDB Freight Limited | Transport & logistics | 2020 |
| IDD Consulting Limited | Professional & scientific | 2023 |
| Idea Factory EN Ltd | Administrative & support | 2012 |
| Idea Prime Construction Ltd | Construction | 2026 |
| Idea Showcases Limited | Professional & scientific | 2004 |
| Ideal Developments (SY) Ltd | Construction | 2014 |
| Ideal GAS Solutionz Ltd | Professional & scientific | 2017 |
| Ideal Paving and Landscaping Ltd | Construction | 2026 |
| Idealbatch Limited | Real estate | 1990 |
| Ideas & Innovation Incubator Ltd | Professional & scientific | 2007 |