| Inspired Woodwork Limited | Construction | 2017 |
| Insta Cure UK Ltd | Real estate | 2016 |
| Insta Keys Ltd | Wholesale & retail | 2025 |
| Installelec Group Ltd | Construction | 2024 |
| Installz Ltd | Wholesale & retail | 2024 |
| Instant Flooring Limited | Extraterritorial | 1992 |
| Instrumentation, Power and Controls Engineering Limited | Manufacturing | 2009 |
| Intada Carpentry Ltd | Manufacturing | 2025 |
| Integral Property Ltd | Construction | 2016 |
| Integrated Bench Ltd | Professional & scientific | 2011 |
| Integrit Systems Ltd | Information & communication | 2009 |
| Intelectrical Solutions Gravesend Ltd | Construction | 2024 |
| Intelinx 1 Ltd | Construction | 2023 |
| Intelligence Network and Propertyservices Limited | Professional & scientific | 2020 |
| Intelligent Lifts & Escalators Limited | Manufacturing | 2011 |
| Intendit Limited | Manufacturing | 2014 |
| Inter Noss Investments Ltd | Financial services | 2022 |
| Inter Trading & Consultancy Limited | Financial services | 2020 |
| Interactive Air Limited | Manufacturing | 2000 |
| Interior Finishers Ltd | Construction | 2011 |
| Internal Communications Network Limited | Information & communication | 1992 |
| International Alliance of Churches and Ministers (Intacam) | Education | 2016 |
| International Blind Tennis Association (Ibta) CIC | Arts & recreation | 2020 |
| International Homestays London Ltd | Hospitality | 2023 |
| International Veterans Cricket Association of India | Arts & recreation | 2020 |
| Interplumb Services Ltd | Construction | 2023 |
| Interventions Alliance Local Partnerships Ltd | Health & social care | 2026 |
| Interventions Alliance Ltd | Public administration | 2024 |
| Intol Ltd | Transport & logistics | 2021 |
| Intraco Ltd | Construction | 2024 |
| Intronet Ltd | Manufacturing | 2016 |
| Investavimas Visiems Ltd | Education | 2025 |
| Investor Express Ltd | Information & communication | 2020 |
| Invicta Advisors Ltd | Information & communication | 2024 |
| Invicta Padel Limited | Arts & recreation | 2025 |
| Invicta SAW Mills (RMC) Limited | Households | 2002 |
| Invictus Heating Services Ltd | Construction | 2017 |
| Invictus Inspection Services Ltd | Professional & scientific | 2021 |
| Invictus Print Management Ltd | Manufacturing | 2019 |
| Inxau Ltd | Financial services | 2024 |
| Ipco Trading Limited | Professional & scientific | 1987 |
| IPS and Co. Limited | Real estate | 2020 |
| Ipss Transport Ltd | Transport & logistics | 2023 |
| IQ Lifts Ltd | Manufacturing | 2024 |
| IR13 Limited | Transport & logistics | 2011 |
| Irawo Living Ltd | Households | 2024 |
| Irfaj UK Ltd | Professional & scientific | 2026 |
| Iron Horse Auto Limited | Wholesale & retail | 2025 |
| Iron Pier Brewery Limited | Manufacturing | 2017 |
| Iron Pier Harbourside Limited | Hospitality | 2024 |
| Iron Style (Kent) Ltd | Wholesale & retail | 2014 |
| Iron Wolf Holdings Ltd | Financial services | 2023 |
| Ironworks Sports Academy CIC | Education | 2025 |
| Irritrak Ltd | Administrative & support | 2024 |
| Irwin Installations Ltd | Construction | 2011 |
| ISA Catering Ltd | Hospitality | 2025 |
| ISA Estate Limited | Real estate | 2019 |
| Isaac James Consultancy Limited | Professional & scientific | 2025 |
| Isandbox Ltd | Education | 2015 |
| ISC Construction Services Ltd | Construction | 2010 |
| Isea Personnel Ltd | Administrative & support | 2024 |
| Isha CEE Child Care Ltd | Health & social care | 2022 |
| Ishook Ltd | Wholesale & retail | 2023 |
| Ishowtimeuk Ltd | Wholesale & retail | 2025 |
| Isma Plumbing & Building Limited | Construction | 2019 |
| Ismen SS Limited | Wholesale & retail | 2020 |
| ISP Haulage Ltd | Transport & logistics | 2019 |
| Istead Associates Ltd | Professional & scientific | 2018 |
| Istead Convenience Store Ltd | Wholesale & retail | 2021 |
| Istead Inn Ltd. | Hospitality | 2019 |
| Italia in Piazza Ltd | Transport & logistics | 2006 |
| Italian Taste Ltd | Hospitality | 2024 |
| ITC Enterprises Limited | Administrative & support | 2010 |
| Itlux Ltd | Information & communication | 2021 |
| Itydata Limited | Information & communication | 2026 |
| Iuliu PAP Ltd | Transport & logistics | 2017 |
| IV Solutions (UK) Limited | Education | 2014 |
| Ivan's Bakery Ltd | Hospitality | 2025 |
| IVY Sport Horses Ltd | Agriculture & fishing | 2024 |
| Ivyhouse Management Limited | Professional & scientific | 2003 |
| Izvoranu Rendering Ltd | Construction | 2010 |
| Izzy Drylining Limited | Construction | 2010 |
| Izzy Global Security Ltd | Administrative & support | 2016 |
| J & F Consulting Services Ltd | Professional & scientific | 2016 |
| J & F Ltd | Real estate | 2021 |
| J & I Chasers Limited | Construction | 1997 |
| J & I Utilities Ltd | Construction | 2024 |
| J & M Crane & Transport Limited | Transport & logistics | 2001 |
| J & N Transport Limited | Transport & logistics | 2019 |
| J & R Fire & Electrical Services Limited | Construction | 2017 |
| J & W Construction (Kent) Ltd | Construction | 2020 |
| J a Maxwell & SON Limited | Other services | 2009 |
| J B Drylining (GB) Ltd | Construction | 2014 |
| J C Penny Ltd | Real estate | 2020 |
| J C Strickland & Sons Limited | Administrative & support | 2006 |
| J C Taping Ltd | Construction | 2017 |
| J Deane Consulting Ltd | Professional & scientific | 2025 |
| J Group Egham Limited | Construction | 2022 |
| J Group Investments Ltd | Financial services | 2021 |
| J Group Ltd | Construction | 2021 |