| Jensco Properties LLP | | 2011 |
| Jessop Events Ltd | Wholesale & retail | 2018 |
| JFR Maxwell Consulting Limited | Professional & scientific | 2024 |
| JK2 Consulting Limited | Professional & scientific | 2023 |
| JKJ Consultancy Limited | Construction | 1980 |
| JM Management Services Ltd | Administrative & support | 2015 |
| JO Care and Beauty Limited | Health & social care | 2023 |
| John J Halls Limited | Administrative & support | 2015 |
| John's Gutters Ltd | Construction | 2018 |
| Joia Consulting Ltd | Professional & scientific | 2017 |
| Joint Ventures (Investments) Limited | Financial services | 2002 |
| Jolimica Properties Limited | Real estate | 2011 |
| Jolinda Holdings Limited | Financial services | 2011 |
| Jolinda Medical Supplies Limited | Wholesale & retail | 1999 |
| Jonathan Shaw Productions Ltd | Information & communication | 2022 |
| JP Newman Medical Ltd | Health & social care | 2018 |
| JS Advisory Limited | Education | 2024 |
| JS Catering Ltd | Hospitality | 2019 |
| JSK Hospitality Ltd | Hospitality | 2024 |
| Jssr Optical Limited | Wholesale & retail | 2017 |
| Juniper Juniors Ltd | Health & social care | 2021 |
| Junipix Limited | Households | 2000 |
| K & H Developments Ltd | Construction | 2015 |
| K SET Designs Ltd | Wholesale & retail | 2018 |
| Kaidex Ventures Limited | Information & communication | 2015 |
| Kaish Enterprises Limited | Real estate | 2020 |
| Kando Consulting Limited | Professional & scientific | 2025 |
| Karakolev Ltd | Transport & logistics | 2020 |
| Karma Tea Co. Limited | Wholesale & retail | 2021 |
| Karmm Properties Limited | Real estate | 2018 |
| Kate Rosamond Bridal Ltd | Manufacturing | 2025 |
| Kayfarb Limited | Other services | 2016 |
| Kelly Creative Ltd | Arts & recreation | 2018 |
| Kennedy Alternative Investments Limited | Real estate | 2019 |
| Kennedy Properties Ltd | Real estate | 2014 |
| Kennedy Trading Limited | Administrative & support | 2009 |
| Kessy Housing Limited | Real estate | 2024 |
| Keysta Ltd | Professional & scientific | 2025 |
| Kharis & Knoble Financial Services Limited | Financial services | 2021 |
| Khsp Road Management Radlett Ltd | Other services | 2016 |
| Kibbutz Representatives | Education | 1986 |
| Killick Associates Ltd | Professional & scientific | 2014 |
| Kings Court (Shenley) Limited | Real estate | 2020 |
| Kipling Street LLP | | 2009 |
| Kirani Holdings Ltd | Real estate | 2020 |
| Kirkstone Trading Limited | Real estate | 2019 |
| Kiteedge Ltd | Information & communication | 2016 |
| Kitt Medical Limited | Health & social care | 2020 |
| Kloof Enterprises Limited | Other services | 2018 |
| Kmauk Projects Limited | Administrative & support | 2006 |
| Knight Hulse Consulting Limited | Professional & scientific | 2025 |
| KOM Playing Cards Ltd | Manufacturing | 2025 |
| Kool Moments Limited | Wholesale & retail | 2023 |
| Kritmatta Limited | Information & communication | 2025 |
| KS (Meica) Consulting Limited | Construction | 2023 |
| KTP UK LLP | | 2004 |
| Kumish Consulting Ltd | Professional & scientific | 2015 |
| KWC Global Ltd | Arts & recreation | 2019 |
| KYN68 Ltd | Construction | 2016 |
| L&L Trasport Solutions Ltd | Transport & logistics | 2025 |
| L&P Certified Accountants Ltd | Professional & scientific | 2025 |
| L'Eauzone Ltd | Professional & scientific | 2004 |
| L.A. Homes Limited | Real estate | 1998 |
| L6LLY Limited | Wholesale & retail | 2021 |
| Laas Vegas Events Ltd | Hospitality | 2022 |
| Lainies Flowers Ltd | Wholesale & retail | 2026 |
| Lance Consultants Limited | Administrative & support | 1992 |
| Land & Marine Investments Limited | Construction | 2003 |
| Landcage LLP | | 2008 |
| Landlords Lawyer Limited | Administrative & support | 2023 |
| Landsoft Limited | Information & communication | 2015 |
| Lantern Insights Ltd | Professional & scientific | 2016 |
| Launch POD Studios Limited | Information & communication | 2020 |
| Laurdan Properties Ltd | Real estate | 2020 |
| Laurenberman Limited | Professional & scientific | 2025 |
| Lawsun International Limited | Professional & scientific | 1996 |
| Lawsun Property Limited | Real estate | 2016 |
| Layda Limited | Administrative & support | 2023 |
| Lazinco Technologies Limited | Information & communication | 2010 |
| LB Plumbing and Heating Contracts Limited | Construction | 2014 |
| LBL Consulting Ltd | Professional & scientific | 2025 |
| LC IT Solutions Limited | Professional & scientific | 2023 |
| Ldhvc Limited | Professional & scientific | 2026 |
| LDN Homes Ltd | Real estate | 2024 |
| LE Chaedoz Financial Services Ltd | Financial services | 2023 |
| LE Kedjenou Ltd | Hospitality | 2016 |
| LE Nails Studio Ltd | Other services | 2024 |
| Lecp Limited | Health & social care | 2023 |
| Leemor Properties Limited | Real estate | 1961 |
| Legendary Television Distribution UK Ltd | Information & communication | 2014 |
| Leniter Ltd | Health & social care | 2019 |
| Leon & Associates Limited | Administrative & support | 2003 |
| Lettings & Property Management Limited | Real estate | 2016 |
| Lewinnick Imaging Consultancy Limited | Professional & scientific | 2025 |
| Lewis Dyson Business Consulting Limited | Professional & scientific | 2007 |
| Life Science Group Limited | Other services | 2008 |
| Life Science Production Limited | Other services | 2013 |
| Lightning in a Bottle Limited | Extraterritorial | 2006 |
| Lilly's Maids Ltd | Administrative & support | 2017 |
| Lily BLU Accessories Limited | Wholesale & retail | 2014 |