| Kerr Family Funerals Ltd | Other services | 2021 |
| Kerriblue Ltd | Professional & scientific | 2024 |
| Kevin G Bownes Photography Limited | Professional & scientific | 2014 |
| Keycharm Limited | Financial services | 2010 |
| Kidbrooke Park Music Festival CIC | Arts & recreation | 2024 |
| Kilfillan Park (Management) Limited | Hospitality | 1992 |
| Kilkenny Homes Ltd | Real estate | 2023 |
| Kind Patches Limited | Wholesale & retail | 2023 |
| King Decor Limited | Construction | 2012 |
| Kingsdown Services Ltd | Professional & scientific | 2017 |
| Kingshill (Berkhamsted) Limited | Professional & scientific | 1995 |
| Kingsted AV Limited | Information & communication | 2018 |
| Kinnity Ltd | Professional & scientific | 2022 |
| Kirstall Associates Limited | Professional & scientific | 2015 |
| Kitchen Compare Ltd | Extraterritorial | 2005 |
| Kite Field Management Company Limited | Professional & scientific | 2014 |
| Kitgrow Limited | Administrative & support | 2019 |
| Kithunters Ltd | Wholesale & retail | 2022 |
| KK Real Estate Consulting Ltd | Real estate | 2024 |
| KKM Transport Services Ltd | Transport & logistics | 2023 |
| Klbc LLP | | 2007 |
| KLC Property Group Ltd | Real estate | 2024 |
| Klogmind Ltd | Professional & scientific | 2024 |
| Kmistry Technology Limited | Financial services | 2021 |
| Knight Lettings Limited | Real estate | 2010 |
| Knight Signs Limited | Other services | 2018 |
| KOA Consulting Limited | Information & communication | 2025 |
| Koha Clinics Limited | Other services | 2019 |
| Komorebi Audio Ltd | Information & communication | 2018 |
| Koru Wellbeing Ltd | Administrative & support | 2019 |
| KP Khoo Foundation | Other services | 2005 |
| Kristian K Ltd | Financial services | 2026 |
| KRT Pro Coaching Ltd | Health & social care | 2025 |
| KRT Projects Limited | Construction | 2012 |
| KTH Outreach Limited | Administrative & support | 2024 |
| KTV Media Ltd | Information & communication | 2015 |
| Kube Rigging Limited | Information & communication | 2014 |
| Kustom Koating (UK) Ltd. | Manufacturing | 2000 |
| KW Rentals Ltd | Real estate | 2017 |
| L K Power Heating Limited | Construction | 2014 |
| L M Straight Smile Ltd | Health & social care | 2019 |
| L&F Vision Ltd | Real estate | 2021 |
| L'Atelier Français CIC | Education | 2025 |
| L.S.P. Services Limited | Administrative & support | 1985 |
| LA Fuga Limited | Manufacturing | 2024 |
| Laap Medical Ltd | Health & social care | 2020 |
| Laboratory Solutions Recruitment Ltd | Administrative & support | 2008 |
| Labyrinth Drives Ltd | Manufacturing | 2020 |
| Laco Holdings Ltd | Construction | 2025 |
| Ladco Pharma Limited | Wholesale & retail | 2013 |
| Lady Lavinia Limited | Information & communication | 2013 |
| Lakem Limited | Other services | 2020 |
| Lamartine Services Ltd | Information & communication | 2023 |
| Lamplight Media Ltd | Professional & scientific | 2022 |
| Lampy Koehler Ltd | Construction | 2023 |
| Landlink (Highfields) Limited | Construction | 2010 |
| Landlink (Stoke Mandeville) Limited | Construction | 2021 |
| Landlink Ltd | Construction | 1982 |
| Langley Logs (Westwood) LLP | | 2026 |
| Lanmak Property Ltd | Construction | 2022 |
| Laprosurge Limited | Health & social care | 1986 |
| Larj Property Limited | Real estate | 2021 |
| Larn Poland Limited | Information & communication | 2005 |
| Lashes by Sharla Limited | Other services | 2025 |
| Latchkey Properties Ltd | Administrative & support | 2025 |
| Latchmore Properties Limited | Construction | 1999 |
| Lathwell Engineering Ltd | Wholesale & retail | 2014 |
| Latymer (Hillcrest) Limited | Construction | 2024 |
| Laureate Management Limited | Households | 2022 |
| Laureate Property Management Ltd | Real estate | 2024 |
| Lavaux Coffee Ltd | Manufacturing | 2024 |
| Laxton Properties (Berkhamsted) Ltd | Construction | 2025 |
| Laxton Properties (Developments) Limited | Professional & scientific | 2016 |
| Laxton Properties (Homes) Ltd | Real estate | 2019 |
| Laxton Properties Limited | Construction | 2008 |
| LCL Wealth Limited | Financial services | 2024 |
| Ldlp Limited | Wholesale & retail | 2003 |
| Leadbetter Associates LLP | | 2025 |
| Leading Teams Ltd | Education | 2018 |
| Learn Happy Education Ltd | Education | 2026 |
| Learnify Global Ltd | Education | 2024 |
| LED Creative Holdings Ltd | Financial services | 2019 |
| LED Creative Ltd | Manufacturing | 2012 |
| Legend Darts Ltd | Arts & recreation | 2018 |
| Legendary Law Limited | Professional & scientific | 2010 |
| Leiff Ltd | Real estate | 2020 |
| LEJ (NI) Developments Limited | Real estate | 2017 |
| Lema Publishing Limited | Information & communication | 1998 |
| Lemontree Recruitment Solutions Ltd | Administrative & support | 2025 |
| Lesley Wilkin & Associates Ltd | Professional & scientific | 2026 |
| Letters&Loom Ltd | Wholesale & retail | 2026 |
| Level 7 Limited | Arts & recreation | 2026 |
| Levo Consulting Ltd. | Administrative & support | 2024 |
| Lewis Developments (Ilmer) Limited | Construction | 2008 |
| Lexfast Services Limited | Administrative & support | 2004 |
| Liam Dempsey Media Group Ltd | Information & communication | 2023 |
| Librados Limited | Professional & scientific | 1997 |
| Lightmonkey Photography Ltd | Professional & scientific | 2019 |
| Lightside Land Consultancy Services Limited | Construction | 2021 |
| Lilern Limited | Professional & scientific | 2015 |