| Home Network Intelligence Limited | Information & communication | 2026 |
| Hoofequine Ltd | Agriculture & fishing | 2013 |
| Hornton Consulting Limited | Professional & scientific | 2014 |
| Horton Investment Group Ltd | Financial services | 2026 |
| Horton Landscape Maintenance Ltd | Administrative & support | 2019 |
| Hospitality Appointments Limited | Administrative & support | 2016 |
| House Nous Ltd | Information & communication | 2022 |
| House of Performanceuk Ltd | Wholesale & retail | 2025 |
| House Properties Limited | Construction | 2024 |
| Howard House Farms LLP | | 2012 |
| Hubflow Consultants Ltd | Information & communication | 2024 |
| Hydronit UK Ltd | Wholesale & retail | 2012 |
| Hælix Ltd | Information & communication | 2024 |
| I S M (Malmesbury) Limited | Hospitality | 1989 |
| Ican Sports Coaching Ltd | Arts & recreation | 2018 |
| Ickis Limited | Other services | 2015 |
| ICS Marine Ltd | Manufacturing | 2015 |
| IF Found Limited | Wholesale & retail | 2024 |
| IF Lost Limited | Professional & scientific | 2008 |
| Ikigai Digital Limited | Professional & scientific | 2021 |
| Ikon Properties Ltd | Real estate | 2024 |
| IN Good Company Holding Ltd | Professional & scientific | 2025 |
| Incapable Staircase C.I.C. | Information & communication | 2020 |
| Indigo Consulting Ltd | Professional & scientific | 2021 |
| Indigo Web Ltd | Information & communication | 2024 |
| Innov Solutions Limited | Professional & scientific | 2011 |
| Inspiredx Ltd | Professional & scientific | 2018 |
| Ironcrest Developments Ltd | Construction | 2026 |
| Irvine Garden Design Limited | Administrative & support | 2018 |
| Istrategic Advisory LLP | | 2010 |
| Istrategic Projects Limited | Financial services | 2017 |
| IVY Design Services Limited | Administrative & support | 2018 |
| IW Products Ltd | Wholesale & retail | 2014 |
| J & D Jackdaws Cafe Ltd | Hospitality | 2020 |
| J Cross Shoes Limited | Real estate | 1988 |
| J Lowe Renovations Limited | Construction | 2020 |
| J&M Flooring (Malmesbury) Ltd | Wholesale & retail | 2017 |
| J. Boulton Window Cleaning Limited | Arts & recreation | 2003 |
| J.J. Arbuthnot & Co. Ltd. | Wholesale & retail | 2020 |
| JAM Communications Limited | Information & communication | 2000 |
| James Designs Limited | Administrative & support | 1988 |
| James Pyle Holdings Ltd | Financial services | 2017 |
| James Pyle Limited | Real estate | 2012 |
| JDP Locum Services Limited | Health & social care | 2015 |
| JEH Retail Ltd | Wholesale & retail | 2023 |
| Jemima Medix Ltd | Health & social care | 2025 |
| Jennifer Cole Accountancy Limited | Professional & scientific | 2013 |
| JHN Homes Ltd | Real estate | 2023 |
| JJ Landscaping & Design Ltd | Administrative & support | 2025 |
| Joden (Builders) Limited | Wholesale & retail | 1993 |
| Jonathan Rose Fine Furniture Limited | Manufacturing | 2004 |
| JPF Resolutions Limited | Professional & scientific | 2011 |
| JS Film Productions Ltd | Information & communication | 2014 |
| Juniper Digital Limited | Professional & scientific | 2021 |
| Just Heating Limited | Administrative & support | 2010 |
| Just Renewables (SW) Limited | Extraterritorial | 2023 |
| Just Wellbeing Ltd | Health & social care | 2024 |
| Kancha Consulting Ltd | Hospitality | 2022 |
| Katifer Collaborative Limited | Households | 2018 |
| Kentsconstruct Ltd | Professional & scientific | 2025 |
| Key Health Solutions Ltd | Manufacturing | 2006 |
| Key Steps Day Nurseries Limited | Education | 2021 |
| Kilmister Consultancy Limited | Professional & scientific | 2013 |
| Kinch Fuel Oils Holdings Limited | Financial services | 2024 |
| Kingfisher Technical Solutions Ltd | Construction | 2009 |
| KM Flower Farm Limited | Agriculture & fishing | 2024 |
| Konigswinter | Education | 2003 |
| L J Cooper & SON Limited | Wholesale & retail | 2002 |
| L.T Elston Garage Ltd | Wholesale & retail | 2023 |
| La&M Retail Limited | Wholesale & retail | 2025 |
| Labarum Health Ltd | Health & social care | 2025 |
| Laetus Land Ltd | Professional & scientific | 2009 |
| Lafoy Limited | Hospitality | 2025 |
| Lakeview Rental Support Ltd | Administrative & support | 2026 |
| Lamor EB Limited | Real estate | 2024 |
| LAND27 Ltd | Wholesale & retail | 2022 |
| Langdale Planning Limited | Professional & scientific | 2019 |
| Lansdown Partners Executive Search Ltd | Administrative & support | 2023 |
| Laser Vision Audio Visual Limited | Construction | 2019 |
| Lavinia Villa Freehold Company Limited | Households | 2020 |
| Laynet Cards LLP | | 2025 |
| LE COQ Gourmand Ltd | Manufacturing | 2025 |
| Legli Limited | Information & communication | 2021 |
| Lemflex Limited | Extraterritorial | 2019 |
| Leon Pretorius Sports Ltd | Arts & recreation | 2020 |
| Leotech Limited | Information & communication | 2014 |
| Leoth Productions Ltd | Information & communication | 2024 |
| Liberis Practice Limited | Real estate | 2007 |
| Lichfield Services and Development Ltd | Manufacturing | 2013 |
| Lifestyle Health & Beauty Ltd | Professional & scientific | 2000 |
| Lightfoot Advisory Ltd | Professional & scientific | 2025 |
| Lily's Barn Dog Training Academy Limited | Professional & scientific | 2021 |
| Lingberg Limited | Construction | 2000 |
| Lite Communications Limited | Professional & scientific | 2013 |
| Little Acers Limited | Health & social care | 2023 |
| LM Affordable Housing Services Ltd | Professional & scientific | 2016 |
| Locke Business Solutions Limited | Professional & scientific | 2015 |
| Locke's Cctv Security Limited | Construction | 2014 |
| Lockstones Estate Agents Ltd | Real estate | 2010 |
| Lockstones Holdings Limited | Financial services | 2025 |