| Khan Clinical Limited | Administrative & support | 2009 |
| Khanam-Byrne Limited | Real estate | 2021 |
| Khansons Properties Limited | Real estate | 2014 |
| Kick OFF Merchants Ltd | Wholesale & retail | 2020 |
| Kieron & Co Barbershop Limited | Other services | 2017 |
| Kifford Capital Ltd | Real estate | 2007 |
| Kilbey Ventures Limited | Other services | 2022 |
| Kilcolman Enterprises Ltd | Construction | 2024 |
| KIN Vintage Ltd | Health & social care | 2019 |
| Kingsland Retreat Ltd | Other services | 2022 |
| Kingsland Stock Ltd | Real estate | 2015 |
| Kingston Vale Properties Limited | Real estate | 2021 |
| Kirkland Services Limited | Administrative & support | 2018 |
| Kj's Welding & Engineering Ltd | Manufacturing | 2024 |
| KJM Silicone Render Ltd | Construction | 2025 |
| KJT Design and Build Ltd | Construction | 2024 |
| KK Upminster Ltd | Hospitality | 2024 |
| Kllm Limited | Professional & scientific | 2024 |
| KLV Engineering Limited | Professional & scientific | 2019 |
| KM Freight Ltd | Transport & logistics | 2021 |
| Kneat Ltd | Wholesale & retail | 2025 |
| Knight Mortgage Solutions Ltd | Extraterritorial | 2022 |
| Knights Invest Ltd | Real estate | 2026 |
| Kodiak Commerce Ltd | Wholesale & retail | 2026 |
| Konig Sportswear Limited | Wholesale & retail | 2018 |
| Konstantinos T Ltd | Information & communication | 2023 |
| Korat Thai Cuisine Limited | Hospitality | 2020 |
| KP Showroom Solutions Limited | Arts & recreation | 2024 |
| KPH Works Ltd | Construction | 2024 |
| KRA Ventures Ltd | Real estate | 2025 |
| KRG Windows Limited | Wholesale & retail | 2019 |
| KRM Catering Ltd | Hospitality | 2025 |
| Krsb Consulting Ltd | Administrative & support | 2022 |
| KSG Contracts Ltd | Construction | 2022 |
| KVN Hair & Beauty Ltd | Other services | 2023 |
| KW Media Enterprises Ltd | Arts & recreation | 2025 |
| Kyice's Kitchen Ltd | Hospitality | 2025 |
| L and O Childcare Ltd | Health & social care | 2025 |
| L J S Electrical Ltd | Construction | 2003 |
| L&A Air Conditioning Ltd | Construction | 2021 |
| L' Amour Nails and Beauty 2 Ltd | Other services | 2023 |
| LA Roche (1949) Limited | Manufacturing | 1949 |
| LAC DES Lesmont UK Limited | Agriculture & fishing | 2021 |
| Ladon Flooring Limited | Construction | 2020 |
| Lafia Holdings UK Limited | Real estate | 2022 |
| Lakhani Legal Limited | Professional & scientific | 2025 |
| Lamb Building Consultancy Ltd | Construction | 2023 |
| Land Sourcing UK Ltd | Administrative & support | 2016 |
| Landmark Facilities UK Limited | Administrative & support | 2022 |
| Lang's Building & Maintenance Ltd | Administrative & support | 2022 |
| Langley Surveying Ltd | Professional & scientific | 2019 |
| Lanmere London (RJC) Limited | Wholesale & retail | 1981 |
| LAS Electrical Services Ltd | Construction | 2026 |
| Lash Properties Ltd | Real estate | 2020 |
| Lash Property Holding Ltd | Real estate | 2021 |
| Lash Real Estate Ltd | Real estate | 2023 |
| Lash Retail Ltd | Wholesale & retail | 2019 |
| Latham Place Management Limited | Households | 2007 |
| Lawack Homes Limited | Construction | 2010 |
| Lawes Investments Ltd | Real estate | 2025 |
| Lccr Ltd. | Other services | 2004 |
| Lcso Holdings Ltd | Financial services | 2020 |
| LDF Holdings Limited | Financial services | 2024 |
| LDN Interiors Ltd | Construction | 2017 |
| LDS Global Limited | Professional & scientific | 2024 |
| Leanne Trotman Limited | Financial services | 2013 |
| Leapfrog Consulting Limited | Education | 2024 |
| Leapmax Consulting Limited | Professional & scientific | 2010 |
| Leapmax Industrials Limited | Wholesale & retail | 2013 |
| Leasingham Hall Limited | Real estate | 2019 |
| Leasingham Hall Site Ltd | Real estate | 2020 |
| LEE Chapel Floors Limited | Professional & scientific | 2012 |
| Leegal Construction and Carpentry Services Limited | Construction | 2022 |
| Lefke Bar and Grill Limited | Hospitality | 2025 |
| Lefke Restaurant Limited | Hospitality | 2016 |
| Legumbi Consulting Limited | Professional & scientific | 2019 |
| Lehsis Limited | Financial services | 2012 |
| LEM Consultancy Solutions Ltd | Administrative & support | 2024 |
| Lenfibreglass Molding. COM Ltd | Manufacturing | 2024 |
| Lets Go Management Ltd | Arts & recreation | 2014 |
| Level UP IT Ltd | Information & communication | 2022 |
| Leviathan Suite Ltd | Manufacturing | 2026 |
| LFP Enterprises Limited | Information & communication | 2016 |
| LFS Design Ltd | Construction | 2025 |
| Lhpt Holdings Ltd | Financial services | 2014 |
| Libava Capital Ltd | Financial services | 2025 |
| Ligeo UK Co. Ltd | Construction | 2015 |
| Lilac One Limited | Real estate | 2019 |
| Lilly Bucks Limited | Hospitality | 2020 |
| Liminal Music Limited | Administrative & support | 2019 |
| Linkmore Business Communications Limited | Administrative & support | 1999 |
| Linnen & Linnen Interiors Limited | Construction | 2018 |
| Lite-Waves CP Services Ltd | Education | 2007 |
| Lite-Waves Therapeutic Education C.I.C. | Education | 2014 |
| Lithuanian Education Centre Studija Ltd | Education | 2011 |
| Little Legs Embroidery Limited | Wholesale & retail | 2019 |
| Little Pink Events Upminster Limited | Wholesale & retail | 2026 |
| Little Pink Flowers Upminster Limited | Wholesale & retail | 2025 |
| Live and Build Limited | Real estate | 2024 |
| LJH Consulting and Training Ltd | Information & communication | 2011 |