| Hydro Cutting Services Limited | Construction | 2016 |
| Hydrogen Fuels Group Ltd | Wholesale & retail | 2020 |
| Hydrogen Refuelling Stations Ltd | Wholesale & retail | 2020 |
| I42 Ltd | Information & communication | 2019 |
| I4B2C Limited | Information & communication | 2012 |
| IAN C Surgey Ltd | Professional & scientific | 2012 |
| IAN Schofield Farrier Limited | Other services | 2014 |
| Ikari Rigging Limited | Arts & recreation | 2025 |
| IKV Tribology Limited | Manufacturing | 2004 |
| ILJ Project Management Limited | Professional & scientific | 2024 |
| Illuminatum Technologies Limited | Professional & scientific | 2019 |
| Impact Coaching and Mentoring Ltd | Administrative & support | 2025 |
| Indoorsout Limited | Construction | 2025 |
| Industrial Athlete Ltd | Construction | 2015 |
| Infiniwave Limited | Real estate | 2023 |
| Infrastruct Ltd | Construction | 2015 |
| Infrastructure Land Consulting Limited | Hospitality | 2012 |
| Inspiremed Limited | Information & communication | 2012 |
| Instant Actions Hosted Services Ltd | Information & communication | 2015 |
| Intelihub Consulting Limited | Professional & scientific | 2015 |
| Invitron Limited | Professional & scientific | 2005 |
| IP Consultants Limited | Information & communication | 2005 |
| Isaac Toothcare Limited | Health & social care | 2025 |
| Italip Limited | Professional & scientific | 2024 |
| Itmilk Limited | Manufacturing | 2016 |
| IUK Systems Limited | Manufacturing | 2007 |
| IVY Cycle Works Ltd | Administrative & support | 2012 |
| J & M Decorators Limited | Construction | 2003 |
| J & PC Medical Limited | Health & social care | 2021 |
| J LEE Construction Ltd | Construction | 2026 |
| J Oliver Plumbing Limited | Construction | 2014 |
| J P Bull Transport Limited | Transport & logistics | 2004 |
| Jacques Enterprise Ltd | Professional & scientific | 2023 |
| James Family Property Limited | Real estate | 2025 |
| James Richard Larner Limited | Professional & scientific | 2025 |
| JAN Hughes Executive Search Ltd | Administrative & support | 2023 |
| Jane Forshaw Ltd | Real estate | 2017 |
| Janus Computers UK Limited | Other services | 1995 |
| Jason Victor Hart Limited | Health & social care | 2019 |
| Jave Properties Limited | Real estate | 2010 |
| JB Group (SW) Ltd | Construction | 2018 |
| JD Personal Finance Ltd | Financial services | 2024 |
| Jenkinson, Steele & Co Ltd. | Professional & scientific | 2023 |
| JJ Gardening Maintenance Limited | Administrative & support | 2014 |
| JJ Window Services Limited | Construction | 2025 |
| JK Machine Tool Services Ltd | Manufacturing | 2023 |
| JKR Price Ltd | Real estate | 2026 |
| JLC Groundwork Contractors Ltd | Construction | 2021 |
| JO Page Inclusion Ltd | Education | 2024 |
| Johnny the Sweep Limited | Construction | 2023 |
| Jolvem Ltd | Wholesale & retail | 2025 |
| Journey Transport Planning Ltd | Professional & scientific | 2013 |
| JP Colewell Limited | Construction | 2025 |
| JP Technical Services Limited | Manufacturing | 2019 |
| JPR Electrical Services Ltd | Construction | 2022 |
| JR CBS Limited | Construction | 2025 |
| JR Contracting Services Ltd | Administrative & support | 2024 |
| JR Planthire Ltd | Administrative & support | 2024 |
| JRB Consultancy Services Ltd | Professional & scientific | 2016 |
| JRM Business Services Ltd | Professional & scientific | 2007 |
| JSJ Supported Living Limited | Health & social care | 2007 |
| JSW Property Holdings Ltd | Real estate | 2024 |
| Julia Bennett Architects Limited | Professional & scientific | 2022 |
| Juniper Events Ltd | Hospitality | 2021 |
| Just Rover Ltd | Wholesale & retail | 2025 |
| JWT Tiling Ltd | Construction | 2025 |
| K & T Green Services Limited | Construction | 2014 |
| Kama Financial Solutions Ltd | Financial services | 2007 |
| Kate Swan Therapy Ltd | Health & social care | 2022 |
| KC Storage Limited | Transport & logistics | 2024 |
| Keymac Services Limited | Administrative & support | 2024 |
| Khans Kebab Ltd | Hospitality | 2025 |
| Kilncan Limited | | 1978 |
| Kings Court Services Limited | Agriculture & fishing | 2003 |
| Kingsmead Flat-Owners (Monmouth) Limited | Households | 1996 |
| KJ & MJ Social Care Ltd | Health & social care | 2025 |
| Kopal Ltd | Hospitality | 2025 |
| Kudu Ltd | Information & communication | 2014 |
| Kutir Monnow Ltd | Hospitality | 2024 |
| Kymin Consultancy Ltd | Other services | 2023 |
| Kytex Ltd | Professional & scientific | 2021 |
| L M Hunter Builders Ltd | Construction | 2017 |
| L.A. Medical Clinic Ltd | Health & social care | 2026 |
| LA Lumiere Ltd | Wholesale & retail | 2016 |
| LA Piccola Monmouth Ltd | Hospitality | 2023 |
| Lakeside Aesthetics Ltd | Other services | 2020 |
| Landscape Connection (UK) Limited | Administrative & support | 2005 |
| Lansdown Construction Ltd | Real estate | 2022 |
| Latorre Consultancy Limited | Manufacturing | 2017 |
| Launch Outdoors Limited | Manufacturing | 2020 |
| Lawrence & Marks Properties Ltd | Real estate | 2021 |
| Layton James Ltd | Professional & scientific | 2021 |
| Leasbrook Associates Ltd | Real estate | 1999 |
| LG Investment Solutions Ltd | Real estate | 2018 |
| Liberty Lane Creative Limited | Wholesale & retail | 2022 |
| Lidbury Partnership Limited | Extraterritorial | 1999 |
| Lidbury Training Limited | Construction | 2002 |
| Liege Manor Equestrian Centre Limited | Arts & recreation | 2013 |
| Liege Manor Equestrian Services LLP | | 2022 |
| Light Power Health Ltd | Health & social care | 2023 |