| KO Payments Ltd | Information & communication | 2019 |
| Ko-Fi Labs Limited | Information & communication | 2017 |
| Koad Limited | Information & communication | 2024 |
| Koei Tecmo Europe Limited | Information & communication | 2002 |
| Kowloon Limited | Wholesale & retail | 2015 |
| Krdl Property Development Limited | Construction | 2023 |
| Kronograph Ltd. | Wholesale & retail | 2021 |
| KTT Comfort Limited | Wholesale & retail | 2014 |
| Kudz Kustomz Ltd | Other services | 2026 |
| Kumarian Ltd | Wholesale & retail | 2015 |
| Kumusha Ekhaya Funeral Services Limited | Manufacturing | 2017 |
| Kura Human Factors Ltd | Professional & scientific | 2018 |
| KWC Property Limited | Real estate | 2019 |
| Kwik-Fit (GB) Limited | Wholesale & retail | 1971 |
| Kwik-Fit Holdings Limited | Professional & scientific | 1940 |
| Kwik-Fit Properties Limited | Construction | 1991 |
| L & P Consultants Ltd. | Information & communication | 2002 |
| L B P Plumbing and Heating Limited | Construction | 2006 |
| L&C Precision Engineering Limited | Manufacturing | 2000 |
| LA Bella Vita Ltd | Wholesale & retail | 2024 |
| LA Peripherals Group Holdings Ltd | Financial services | 2023 |
| Ladygrove Minsden Ltd | Professional & scientific | 2018 |
| Lambda Lifters Ltd | Transport & logistics | 2026 |
| Land 149 Arlesey Road Limited | Real estate | 2021 |
| Lantern Building Residents Management Company Limited | Households | 2006 |
| Lasidore Cosmetics Ltd | Other services | 2014 |
| Last Dog Films Ltd | Information & communication | 2026 |
| Lavanda Holdings Limited | Hospitality | 2022 |
| Lavender Medical Limited | Health & social care | 2009 |
| Laxsiv Limited | Professional & scientific | 2021 |
| Layher Limited | Wholesale & retail | 1987 |
| LBO International Holding Ltd | Financial services | 2026 |
| Leadermans Limited | Extraterritorial | 2002 |
| Leadermans Property Management Limited | Real estate | 2010 |
| Learn Interactive Ltd | Other services | 2021 |
| LEARN4YOU Limited | Hospitality | 2025 |
| LEE Saunders London Limited | Manufacturing | 2021 |
| Legal SS Ltd | Professional & scientific | 2019 |
| Letchworth (Norton School) Management Company Limited | Households | 2007 |
| Letchworth Autoway Centre Limited | Wholesale & retail | 1974 |
| Letchworth Business Centre Limited | Real estate | 2024 |
| Letchworth Carpet Centre Ltd | Wholesale & retail | 2025 |
| Letchworth Civic Trust | Health & social care | 1914 |
| Letchworth Cricket Club Limited | Arts & recreation | 2004 |
| Letchworth Diamond Wheels Ltd | Wholesale & retail | 2024 |
| Letchworth Garage Holdings Ltd | Financial services | 2025 |
| Letchworth Garden City Business Improvement District Limited | Other services | 2014 |
| Letchworth Garden City Community Group | Hospitality | 2004 |
| Letchworth Garden City IT Limited | Information & communication | 2024 |
| Letchworth Garden City Trading Limited | Information & communication | 1998 |
| Letchworth Garden Shed CIC | Administrative & support | 2022 |
| Letchworth General Services Limited | Administrative & support | 2026 |
| Letchworth Golf Trust Limited | Arts & recreation | 1905 |
| Letchworth Housing Investments Limited | Financial services | 2010 |
| Letchworth Palace Limited(The) | Construction | 1924 |
| Letchworth Rugby Club Trading Limited | Arts & recreation | 2025 |
| Letchworth Sports and Tennis Club Ltd | Arts & recreation | 2013 |
| Letchworth Wines Ltd | Wholesale & retail | 2021 |
| Letting Go Limited | Real estate | 2024 |
| Levant Foods Europe Ltd | Hospitality | 2025 |
| Levant Foods Trading Ltd | Hospitality | 2025 |
| Level 7 Expertise Limited | Administrative & support | 2016 |
| Lewisgough Ltd | Transport & logistics | 2025 |
| Leys Barber Ltd | Other services | 2025 |
| Leys Kebab Ltd | Hospitality | 2024 |
| Leysmundo Limited | Professional & scientific | 2014 |
| LGC Capital Ltd | Real estate | 2024 |
| LGC Enterprise Limited | Wholesale & retail | 2016 |
| Liam Sherar Radiation Consultancy Ltd | Professional & scientific | 2026 |
| Lifecare Chemi Limited | Wholesale & retail | 2011 |
| Light & Cook Ltd | Hospitality | 2022 |
| Lighthouse Planning Ltd | Real estate | 2015 |
| Lighthouse Staffing Solutions Ltd | Administrative & support | 2024 |
| Lilypad Property Investments Ltd | Real estate | 2025 |
| Limni Ltd | Professional & scientific | 2025 |
| Linea Research Holdings Ltd | Financial services | 2018 |
| Linea Research Limited | Professional & scientific | 2003 |
| Linteriors Limited | Arts & recreation | 2006 |
| Liquid Lens Systems Limited | Administrative & support | 2016 |
| List My Garage Limited | Administrative & support | 2017 |
| Little Acorns Wraparound Care Ltd | Health & social care | 2025 |
| Little Hampden Consulting Limited | Professional & scientific | 2024 |
| Little Latte's Coffee & Play Limited | Hospitality | 2023 |
| LIZ ROE Ltd | Administrative & support | 2013 |
| Lloret Care Ltd | Public administration | 2026 |
| Lloyd Parry Limited | Extraterritorial | 2012 |
| Lloyds Heritage Limited | Wholesale & retail | 2023 |
| Lmbu Limited | Construction | 2020 |
| LMO Food Science Ltd | Wholesale & retail | 2025 |
| LMS Welding and Engineering Ltd | Professional & scientific | 2021 |
| Local Counselling Centre Limited | Health & social care | 2011 |
| Logic Industrial Ltd | Real estate | 2023 |
| Logic Land & Property Limited | Real estate | 2013 |
| Logic Property Investment Ltd | Real estate | 2020 |
| Logic Rent Ltd | Hospitality | 2020 |
| London Arrangements Limited | Information & communication | 2016 |
| London Damp Company Limited | Construction | 2022 |
| London Fire Stopping Limited | Public administration | 2019 |
| London Quant Limited | Education | 2007 |
| London Spine Unit Limited | Health & social care | 2010 |