| Janzai Ltd | Wholesale & retail | 2020 |
| JAX Hygiene and Facial Aesthetics Ltd | Health & social care | 2025 |
| JCH Group Holdings Ltd | Financial services | 2025 |
| JCH Partnered Solutions Ltd | Professional & scientific | 2025 |
| JCH Richmond Ltd | Arts & recreation | 2025 |
| JCM Faulkner Consultancy Ltd | Health & social care | 2015 |
| Jcpb Consulting Ltd | Information & communication | 2019 |
| JD Letting Property Ltd | Real estate | 2022 |
| Jeffreys Road NO 57 Limited | Households | 2008 |
| JG Residential Ltd | Real estate | 2026 |
| JIS Engineering Ltd. | Manufacturing | 2012 |
| JIS Systems Limited | Professional & scientific | 2010 |
| Jjepga Limited | Professional & scientific | 2009 |
| JK 2018 Limited | Wholesale & retail | 2024 |
| Jlcc Limited | Professional & scientific | 2009 |
| Joanne's Nails HN Ltd | Other services | 2025 |
| John Campion Consulting Limited | Professional & scientific | 2017 |
| Jojo Hair Stylist Ltd | Other services | 2024 |
| JR CT Consulting Limited | Professional & scientific | 2025 |
| JRJ Consulting Ltd | Professional & scientific | 2025 |
| JS Customz Ltd | Wholesale & retail | 2025 |
| JT Beer Limited | Professional & scientific | 2015 |
| Julia Wilkinson Consultancy Ltd | Real estate | 2025 |
| Just Nuts Films Limited | Information & communication | 2007 |
| JUST4DOGS Limited | Other services | 2025 |
| Justin Barr Ltd | Health & social care | 2017 |
| K.S.London Limited | Wholesale & retail | 2012 |
| Kalergo Ltd | Financial services | 2013 |
| Kantara Initiative Ltd | Professional & scientific | 2022 |
| Keen Jewellery Ltd. | Wholesale & retail | 1995 |
| Kestrel Energy Solutions Ltd | Mining & quarrying | 2018 |
| KEW Property Management Limited | Real estate | 2015 |
| Kilner Group Limited | Hospitality | 2016 |
| Kinellan Ltd | Hospitality | 2025 |
| King's Church Kingston | Other services | 2014 |
| Kings Meadow (Surrey) Management Company Limited | Households | 2026 |
| Kingsmarkham Enterprises Limited | Arts & recreation | 1976 |
| Kinord Business Consultants Limited | Administrative & support | 2016 |
| Klic Properties Limited | Real estate | 2017 |
| Knight James Associates Ltd | Administrative & support | 2011 |
| Knight James Limited | Administrative & support | 2000 |
| Kops Investment Ltd | Financial services | 2025 |
| Kotj Clothing Limited | Wholesale & retail | 2022 |
| KRY10 UK Ltd | Information & communication | 2025 |
| L K Legal Limited | Professional & scientific | 2013 |
| LA FÉE Papillon Ltd | Information & communication | 2026 |
| Laclede Limited | Professional & scientific | 2020 |
| Lakehouse Consulting Ltd | Information & communication | 2024 |
| Laldas Limited | Wholesale & retail | 2003 |
| Landlab London Limited | Professional & scientific | 2018 |
| Lavender Mews Property Limited | Construction | 2018 |
| Lawns to Landscapes Ltd | Administrative & support | 2011 |
| Lead Alliance Ltd | Professional & scientific | 2026 |
| Leamore Investments Limited | Real estate | 1954 |
| LEE Design Associates Limited | Professional & scientific | 1979 |
| Legacy Crafters Ltd | Construction | 2026 |
| Lennox Costume Limited | Other services | 2023 |
| LEX TV Ltd. | Information & communication | 2017 |
| Lifeplan TD Limited | Financial services | 2017 |
| Lighting Engine Holdings Limited | Administrative & support | 2017 |
| Lightway Productions Limited | Information & communication | 2023 |
| Lime Group Holdings Ltd | Construction | 2023 |
| Lime Showrooms Limited | Construction | 2009 |
| Limitededitiondesign.Co.Uk Ltd | Professional & scientific | 2011 |
| Limp Brisket Ltd | Hospitality | 2020 |
| Lindenhall Investments Limited | Construction | 1972 |
| Lindenhall Ventures Ltd | Administrative & support | 2013 |
| Lingham Street Management Ltd | Households | 2014 |
| Lingwood Developments Ltd | Real estate | 2018 |
| Liquintel Ltd | Professional & scientific | 2025 |
| Liscon Ltd | Professional & scientific | 2016 |
| Litten Holdings Ltd | Real estate | 2024 |
| Little Heroes Nurseries Ltd | Health & social care | 2021 |
| LJC Global Limited | Administrative & support | 2024 |
| LK & Associates Limited | Professional & scientific | 2012 |
| Lockett Estates International Limited | Real estate | 2013 |
| Lockett Property Management Limited | Real estate | 2012 |
| London Play Centres Ltd | Arts & recreation | 2018 |
| Long MAN Real Estate Limited | Professional & scientific | 2025 |
| Lost in Design Ltd | Professional & scientific | 2024 |
| Lotus Tree Ltd | Wholesale & retail | 2022 |
| Lovalot Productions Ltd | Information & communication | 2020 |
| LSL Physiotherapy Ltd | Health & social care | 2012 |
| Lucky Fellow Limited | Professional & scientific | 2018 |
| Lucror Estates 1 Limited | Real estate | 2024 |
| Lumin Homes Ltd | Real estate | 2014 |
| Luxalma Ltd | Administrative & support | 2026 |
| Lynchmere Consulting (2022) Limited | Professional & scientific | 2022 |
| Lynnette Lawrance Consulting Limited | Information & communication | 2018 |
| M.C.King & Co Limited | Construction | 2005 |
| Mackenzie Stallard Limited | Construction | 2025 |
| Madeva Investments Limited | Professional & scientific | 2011 |
| Madonnas Investments Ltd | Real estate | 2009 |
| Maeve Walsh Consulting Ltd | Professional & scientific | 2018 |
| Magic FOX Limited | Information & communication | 2002 |
| Magpie Makes Limited | Arts & recreation | 2014 |
| Make Fit Happen Limited | Arts & recreation | 2017 |
| Make YOU Shine Ltd | Wholesale & retail | 2020 |
| Mandt Education Ltd | Information & communication | 2024 |
| Mango Vibe Limited | Arts & recreation | 2009 |