| Imagex Limited | Health & social care | 2026 |
| Immigrantnewsuk Limited | Information & communication | 2025 |
| Imogen Allen Ltd | Professional & scientific | 2026 |
| Impetus Environmental Trust | Administrative & support | 2006 |
| IN the Moment (London) Ltd | Information & communication | 2017 |
| Incite Education CIC | Education | 2025 |
| Indigo Blue Freeholds Ltd | Real estate | 2016 |
| Infinite Freedom Enterprises LLP | | 2021 |
| Infinity Football Ltd | Education | 2019 |
| Infinity Healthcare North Ltd | Health & social care | 2023 |
| Informed Services Ltd | Information & communication | 2016 |
| Infosec Consulting Limited | Information & communication | 2008 |
| Ingleby Bloodstock Limited | Arts & recreation | 2014 |
| Ingleby Estates Ltd | Hospitality | 2016 |
| Inhouse Architecture Limited | Professional & scientific | 2012 |
| INK Drop Shop Ltd | Wholesale & retail | 2024 |
| Innerglow Collective Skin Health Ltd | Other services | 2024 |
| Innovate D&B Limited | Construction | 2019 |
| Innovate Design Develop Deliver Limited | Construction | 2022 |
| Insight Health Evaluation Limited | Professional & scientific | 2026 |
| Inspired Property London LLP | | 2019 |
| Inspiron Studios Ltd | Professional & scientific | 2026 |
| Instrument Pipework Services Limited | Professional & scientific | 2011 |
| Integrifire Ltd | Professional & scientific | 2024 |
| Intellibin Limited | Professional & scientific | 2018 |
| Interacting UK Limited | Education | 2010 |
| Interactive Secretarial Services Limited | Administrative & support | 2007 |
| Interlink Deal Sourcing Limited | Real estate | 2024 |
| Interlink Property Projects Limited | Real estate | 2024 |
| Interlink Property Solutions Limited | Real estate | 2024 |
| International Community of Syrian Radiologists Ltd | Education | 2025 |
| Intrepid Fabrication Limited | Construction | 2019 |
| Invicta Asset Management Limited | Other services | 2014 |
| Ipsw Ltd | Real estate | 2018 |
| IR Financial Limited | Financial services | 2019 |
| Iraznaz Ltd | Wholesale & retail | 2023 |
| Iron Guidance Limited | Education | 2010 |
| Isdrad Limited | Health & social care | 2026 |
| Isea Consultancy Ltd | Health & social care | 2023 |
| Itchyrobot UK Limited | Information & communication | 2010 |
| IVY Delivery Consulting Ltd | Information & communication | 2026 |
| J & C Mann and J Thompson WP Ltd | Administrative & support | 2024 |
| J & D Products Limited | Wholesale & retail | 2002 |
| J & J Macrae WP Ltd | Administrative & support | 2024 |
| J Burton & T Pilkington WP Ltd | Professional & scientific | 2024 |
| J E Property Developments (North East) Limited | Construction | 2019 |
| J Gilpin & S Mhuircheartaigh WP Ltd | Administrative & support | 2024 |
| J Lees Developments Ltd. | Construction | 2005 |
| J Lyons Consultancy Limited | Administrative & support | 2016 |
| J Malone Civils Ltd | Construction | 2020 |
| J Nertney Ltd | Professional & scientific | 2025 |
| J Shears Family Holdings Ltd | Real estate | 2020 |
| J Shears Family Partnership LLP | | 2020 |
| J Shepard WP Ltd | Administrative & support | 2024 |
| J&K Rigging Limited | Extraterritorial | 2018 |
| J&M Qa/Qc Services Limited | Professional & scientific | 2022 |
| J. G. (Aldburgh) Limited | Administrative & support | 1974 |
| JA Prop LLP | | 2019 |
| JA Propco Ltd | Real estate | 2019 |
| JAD Leisure Solutions Ltd | Hospitality | 2009 |
| JAG Property Management Partnership LLP | | 2021 |
| Jags Group LLP | | 2022 |
| Jaka Family Partnership LLP | | 2020 |
| Jaka Properties Limited | Real estate | 2018 |
| Jameela Associates Ltd | Health & social care | 2023 |
| James a Wallace Consultancy Ltd | Information & communication | 2016 |
| Jamie Orrell Design Ltd | Arts & recreation | 2025 |
| Jason Neeson Limited | Professional & scientific | 2021 |
| Jaspia Contracts Ltd | Households | 2024 |
| Jaspia Holdings Ltd | Real estate | 2021 |
| Jaspor Ltd | Real estate | 2019 |
| Jassal Family Holdings Limited | Real estate | 2018 |
| Jassal Family Partnership LLP | | 2018 |
| JBR Group Limited | Financial services | 2024 |
| JC Musgrave Capital Limited | Professional & scientific | 2019 |
| JC Musgrave Limited | Construction | 2005 |
| JCK Houses Ltd | Real estate | 2025 |
| JCM Agriculture and Leisure Ltd | Agriculture & fishing | 2022 |
| JCM Environmental Services Limited | Construction | 2008 |
| JCM Environmental Surveys Limited | Water & waste | 2006 |
| JCM Estates Management Limited | Real estate | 2016 |
| JCM Holdings Limited | Professional & scientific | 2001 |
| JCM Land Ltd | Construction | 2021 |
| JCM Overage Limited | Financial services | 2018 |
| JCM Plant Limited | Administrative & support | 2020 |
| JCM Property Consultants Limited | Professional & scientific | 2013 |
| JCM Retail Equipment Limited | Wholesale & retail | 1997 |
| Jenya Property Partnership LLP | | 2022 |
| Jera Projects Ltd | Professional & scientific | 2024 |
| JH Assets Ltd | Real estate | 2025 |
| JHL Home Solutions Ltd | Real estate | 2021 |
| JJN Estates Ltd | Hospitality | 2024 |
| JJP (EA) Holdings Ltd | Real estate | 2022 |
| JJP (EA) LLP | | 2022 |
| JKW Management Limited | Real estate | 2022 |
| JL Pipe Solutions Limited | Manufacturing | 2025 |
| JLA Engineering Ltd | Professional & scientific | 2023 |
| JLI Construction Ltd | Construction | 2025 |
| JLM Assessment Services Ltd | Health & social care | 2025 |
| JLM Building Ltd | Construction | 2019 |