| Inspired Brands Holding Company Ltd | Financial services | 2023 |
| Inspiring Services Ltd | Construction | 2025 |
| Integra Global Solutions UK Limited | Information & communication | 2009 |
| Intelligain Ltd | Extraterritorial | 2017 |
| Intelligentmaths Ltd | Education | 2016 |
| Inter Group Holdings Limited | Financial services | 2007 |
| Interbuild Projects Limited | Construction | 2009 |
| Interclean First Services Limited | Administrative & support | 2005 |
| Interhus Investments Ltd | Real estate | 2020 |
| Interior Fittings UK Ltd | Construction | 2016 |
| Interiovibe Ltd | Professional & scientific | 2024 |
| International Association of Paranthan H M V Old Students C.I.C. | Other services | 2016 |
| International Certification Ltd | Education | 2019 |
| International Gospel Media Ltd | Arts & recreation | 2021 |
| International Validators for Certification Bodies (Europe) Limited | Administrative & support | 2010 |
| Intovate Ltd | Financial services | 2020 |
| Intrinsicm Limited | Professional & scientific | 2013 |
| Intune Communications and Entertainment Ltd | Professional & scientific | 2020 |
| Involvant Limited | Real estate | 2020 |
| Iosif Catering Limited | Hospitality | 2023 |
| IP Construct Limited | Information & communication | 2008 |
| Iplog IT Solutions Limited | Information & communication | 2019 |
| Ipro Enterprises Ltd | Professional & scientific | 2024 |
| Iprompt Limited | Information & communication | 2008 |
| IQ Technology Limited | Professional & scientific | 2022 |
| Irenne Ltd | Wholesale & retail | 2023 |
| Irfan Jamil Ltd | Wholesale & retail | 2023 |
| Isaak Estates LLP | | 2024 |
| Isafe Reality Ltd | Professional & scientific | 2021 |
| Isalem Limited | Arts & recreation | 2003 |
| Ishuh Consulting Limited | Information & communication | 2021 |
| ISK Properties Limited | Real estate | 2020 |
| Islamecom Ltd | Wholesale & retail | 2025 |
| Isocial Ltd | Manufacturing | 2015 |
| Isystango Ltd | Information & communication | 2020 |
| IT Tech Services Ltd | Information & communication | 2024 |
| IT Titans Limited | Information & communication | 2023 |
| It's ALL in the Detail Ltd | Wholesale & retail | 2020 |
| It's Genius Ltd | Financial services | 2020 |
| It's Going to Happen Limited | Information & communication | 2023 |
| It's MOW Time - Garden & Tree Services Ltd | Administrative & support | 2022 |
| Itachio Limited | Wholesale & retail | 2018 |
| Italian Claygate Limited | Hospitality | 2021 |
| Italian Gusto Ltd | Hospitality | 2026 |
| Itconvert Ltd | Professional & scientific | 2019 |
| Itech 24 Ltd | Information & communication | 2019 |
| Itforge Ltd | Information & communication | 2020 |
| Ithaca Consultancy Ltd | Professional & scientific | 2021 |
| Itransform Ltd | Administrative & support | 2014 |
| Iuli Trans Ltd | Transport & logistics | 2014 |
| Ivan Moore Consultancy Limited | Professional & scientific | 2010 |
| Ivey Properties Ltd | Real estate | 2017 |
| Ivory Workforce Limited | Construction | 2026 |
| IVY Heights Group Ltd | Real estate | 2025 |
| Iwbs Plumbing & Heating Ltd | Construction | 2007 |
| J & B Drive Specialists Limited | Construction | 2013 |
| J & B Drives and Building Limited | Construction | 2024 |
| J & J Cleaning Limited | Other services | 2001 |
| J & K (Ruislip) Limited | Wholesale & retail | 2017 |
| J & K Autos Limited | Wholesale & retail | 2006 |
| J & M Contractors (Bucks) Limited | Construction | 2007 |
| J & M Electrical Limited | Construction | 2005 |
| J & M Pavers Limited | Construction | 2006 |
| J & P Professional Services Limited | Professional & scientific | 2018 |
| J a Hine Ltd | Professional & scientific | 2013 |
| J a Removal Services Limited | Transport & logistics | 2019 |
| J Cannon Services Ltd | Other services | 2018 |
| J G Consultants Limited | Professional & scientific | 2014 |
| J Henley Ltd | Education | 2023 |
| J I Property Managment Ltd | Real estate | 2018 |
| J K Investments London Ltd | Real estate | 2016 |
| J Mccarthy Property Care Limited | Construction | 2024 |
| J Mechanical Ltd | Construction | 2016 |
| J Morris & Sons Limited | Construction | 2011 |
| J N F Plant & Commercial Ltd | Administrative & support | 2018 |
| J P W Homecare Solutions Limited | Construction | 2019 |
| J Rose Construction Ltd | Information & communication | 2022 |
| J T Contractors Ltd | Construction | 2009 |
| J&I Cleaning Services Ltd | Administrative & support | 2009 |
| J&I Deep Cleaning Services Limited | Administrative & support | 2018 |
| J&L Traders Ltd | Wholesale & retail | 2013 |
| J&M Crystal Finish Ltd | Wholesale & retail | 2025 |
| J&M Pharma Limited | Health & social care | 2012 |
| J&P Appliance Limited | Wholesale & retail | 2025 |
| J&S Capital Ltd | Real estate | 2026 |
| J&S Carpentry Limited | Construction | 2017 |
| J&S Tipper Hire Ltd | Administrative & support | 2024 |
| J'N'M Care Agency Ltd | Health & social care | 2019 |
| J-Cisnetco Solutions Ltd | Information & communication | 2010 |
| J.A. Stott (Carpentry) Employees’ Trustees Limited | Construction | 2021 |
| J.A. Stott (Carpentry) Limited | Construction | 1993 |
| J.P.B Electrics Limited | Construction | 2018 |
| J.Paul & Co Limited | Wholesale & retail | 2013 |
| JA Inspired Property Limited | Real estate | 2025 |
| Jaagili Limited | Information & communication | 2025 |
| Jabo Ltd | Information & communication | 2007 |
| Jacalfie Ltd | Wholesale & retail | 2017 |
| Jacijae Ltd | Health & social care | 2018 |
| Jack Harvey London Ltd | Wholesale & retail | 2017 |
| Jackdaw Group Ltd | Financial services | 2020 |