| Hyway Cabling Ltd | Energy | 2014 |
| HZ Venture Management Ltd | Hospitality | 2022 |
| HZB Limited | Professional & scientific | 2024 |
| I & O Investments Ltd | Real estate | 2023 |
| I & S Rishad Ltd | Real estate | 2017 |
| I AM the Voice International Ltd | Health & social care | 2023 |
| I and I Catering Food PVT Limited | Hospitality | 2023 |
| I C I Finance Limited | Financial services | 1895 |
| I Glazing Ltd | Construction | 2012 |
| I M Investments Ltd | Administrative & support | 2002 |
| I Matter Social Care Limited | Health & social care | 2023 |
| I Point Accessories Ltd | Wholesale & retail | 2024 |
| I Point Phones and Computers Limited | Wholesale & retail | 2025 |
| I Repair Computers Ltd | Other services | 2024 |
| I S a Store Limited | Wholesale & retail | 2002 |
| I&A Cleaning Services Limited | Administrative & support | 2024 |
| I&D Developers Ltd | Real estate | 2026 |
| I&K Property Management Limited | Real estate | 2021 |
| I&M Construct Ltd | Construction | 2020 |
| I-Bytes (UK) Ltd | Information & communication | 2010 |
| I-Care Support Ltd | Administrative & support | 2018 |
| I-Cut Barbieri Ltd | Other services | 2019 |
| I-Perceptions Consulting Limited | Professional & scientific | 2017 |
| I-Saii Ltd | Health & social care | 2026 |
| I. Bivol Ltd | Construction | 2018 |
| I.B.M Consult International Ltd | Professional & scientific | 2020 |
| I.D.S Slough Ltd | Transport & logistics | 2026 |
| I.Deliver Logistics Limited | Transport & logistics | 2025 |
| I4BT Limited | Real estate | 2025 |
| IA Consultancy Services Ltd | Professional & scientific | 2015 |
| Iaao Consulting Ltd | Professional & scientific | 2016 |
| IAB Logistics Ltd | Construction | 2017 |
| Iabel Ltd | Wholesale & retail | 2024 |
| IAC Accountants Limited | Professional & scientific | 2013 |
| Iacub Transporter Ltd | Transport & logistics | 2019 |
| Iaecsp Limited | Administrative & support | 2019 |
| IAG Solutions Ltd | Information & communication | 2019 |
| IAH Properties Ltd | Construction | 2017 |
| IAM Gardening Services Limited | Administrative & support | 2018 |
| IAM4U Ltd | Health & social care | 2026 |
| IAN Horrocks-Taylor Limited | Professional & scientific | 2003 |
| IAN Jacob Healthcare Limited | Health & social care | 2014 |
| Ianss Ltd | Financial services | 2019 |
| Ianss Motors Ltd | Wholesale & retail | 2019 |
| Iasalecentre Ltd | Wholesale & retail | 2026 |
| IAU Ltd | Wholesale & retail | 2023 |
| Ibbotson Court Limited | Households | 2011 |
| Iberian Mining Limited | Mining & quarrying | 2005 |
| Ibex Tradings Ltd | Wholesale & retail | 2025 |
| IBI Energy Ltd | Construction | 2024 |
| Ibiz 1 Ltd | Wholesale & retail | 2025 |
| Ibmail Logistics Cargo Limited | Transport & logistics | 2025 |
| Ibn-Sinna Ltd | Construction | 2010 |
| Ibooth London Limited | Administrative & support | 2013 |
| Ibraheem Prime Services Limited | Transport & logistics | 2013 |
| Ibrahim Capital Property Ltd | Real estate | 2026 |
| Ibraqmar Ltd | Wholesale & retail | 2025 |
| IC Ludgate Limited | Financial services | 2017 |
| Icautosslough Ltd | Wholesale & retail | 2024 |
| Icebright Ltd | Health & social care | 2023 |
| Iceman Ltd | Hospitality | 2025 |
| Icey Rolls Ltd | Hospitality | 2016 |
| ICG Construction Ltd | Construction | 2022 |
| ICI Chemicals & Polymers Limited | Real estate | 1940 |
| Ickenham PUB Company Ltd | Hospitality | 2025 |
| Icleanly Ltd | Administrative & support | 2025 |
| Icloud Tech Limited | Information & communication | 2023 |
| Icon Roofing Services Ltd | Construction | 2025 |
| Icon Shopping Ltd | Administrative & support | 2025 |
| Iconic DJS Limited | Arts & recreation | 2011 |
| Icraft Electrical Services Ltd | Construction | 2023 |
| Icubes Tech Limited | Manufacturing | 2014 |
| ID Consultants Ltd | Professional & scientific | 2026 |
| Ida's Travel Ltd | Administrative & support | 2019 |
| Idda Care Ltd | Health & social care | 2022 |
| Ideal Hajj & Umrah Ltd | Administrative & support | 2018 |
| Ideal Homeware Limited | Wholesale & retail | 2010 |
| Ideal Ideas Ltd | Wholesale & retail | 2017 |
| Ideal Traders Ltd | Wholesale & retail | 2021 |
| Ideal Wedding Ltd | Administrative & support | 2025 |
| Idealsolutions Consultancy Ltd | Professional & scientific | 2024 |
| Ideas Linens Limited | Wholesale & retail | 2025 |
| Idesign Innovations Limited | Wholesale & retail | 2016 |
| Idha Software Solutions Limited | Information & communication | 2008 |
| IDQ Homes Ltd | Real estate | 2024 |
| Idream International Limited | Professional & scientific | 2026 |
| Iduk Group Limited | Arts & recreation | 2022 |
| IDX Technology Europe, Ltd. | Manufacturing | 1994 |
| IE Architecture Ltd | Professional & scientific | 2017 |
| IEA Media Ltd | Information & communication | 2014 |
| Ifedinma G Limited | Health & social care | 2022 |
| Iffah Foods Limited | Hospitality | 2023 |
| Ifill Fittings Services Ltd | Construction | 2026 |
| Ifix Homes Ltd | Construction | 2016 |
| IG Financials Limited | Professional & scientific | 2016 |
| IGE Services Ltd | Professional & scientific | 2021 |
| Ignite Print Solutions Ltd | Manufacturing | 2010 |
| Ignite Pro 365 Limited | Real estate | 2025 |
| Iguoton Collective Ltd | Professional & scientific | 2021 |
| IH London Limited | Wholesale & retail | 2019 |