| KSP1 (Northampton) Ltd | Real estate | 2025 |
| KSP2 (Northampton) Ltd | Real estate | 2025 |
| KWT (UK) Ltd | Agriculture & fishing | 2003 |
| Labrapack Limited | Administrative & support | 2019 |
| Laelo Limited | Wholesale & retail | 2026 |
| Lambert Place Management Company Limited | Households | 2006 |
| Lambournes (Sophos) Limited | Professional & scientific | 1980 |
| Lampot Properties Limited | Real estate | 2008 |
| LAN Survey Services Ltd | Professional & scientific | 2020 |
| Langford Digital Advisory Ltd | Professional & scientific | 2026 |
| Langham Engineering Limited | Manufacturing | 1985 |
| Lania Holdings Limited | Hospitality | 2019 |
| Larchwood Contracts Ltd | Construction | 1999 |
| Launde Park Farm Ltd | Information & communication | 2021 |
| Lawson Consulting Limited | Information & communication | 2007 |
| Lazy Bone Films Ltd | Information & communication | 2019 |
| LE Chameau Holdings Limited | Professional & scientific | 2012 |
| LE Chameau UK Limited | Wholesale & retail | 2012 |
| Leadertree Consulting Ltd | Professional & scientific | 2018 |
| Leadlinx Limited | Wholesale & retail | 2025 |
| Learn Well Trading Limited | Wholesale & retail | 2016 |
| Learning Farm Owston CIC | Education | 2011 |
| Legends LAB Limited | Information & communication | 2017 |
| Leiwan Ltd | Hospitality | 2021 |
| Leoni's QUO Vadis Limited | Professional & scientific | 1969 |
| Lewis J Champion Ltd | Other services | 2019 |
| Leyimainfosys Limited | Information & communication | 2009 |
| LHB Services Ltd | Professional & scientific | 2016 |
| Libertas Networks Limited | Wholesale & retail | 2022 |
| Lidbetter and Hicks Limited | Construction | 1994 |
| Life for Love Ltd | Information & communication | 2024 |
| Life Rituals Ltd | Professional & scientific | 2017 |
| Lilo & Beau Limited | Real estate | 2025 |
| Lily Rose & Bubbles Limited | Wholesale & retail | 2018 |
| Limfax Properties Limited | Real estate | 1997 |
| Limitless Performance Centre Ltd | Arts & recreation | 2025 |
| Lindy Shearer Break Free Limited | Health & social care | 2026 |
| Line Xero Limited | Information & communication | 2011 |
| Linecross Composites Limited | Extraterritorial | 1999 |
| Linecross Group Limited | Professional & scientific | 2003 |
| Linecross Limited | Manufacturing | 1990 |
| Linky UK Limited | Extraterritorial | 1989 |
| Lionbridgepr Ltd | Professional & scientific | 2007 |
| Little Angels (Uppingham) Limited | Education | 2009 |
| Little Barn Court Holdings Limited | Hospitality | 2009 |
| Little County Breaks Ltd | Real estate | 2024 |
| Littlewood Marketing Consultancy Limited | Professional & scientific | 2009 |
| Livelab Limited | Professional & scientific | 2005 |
| Living Locations Limited | Other services | 1993 |
| Living Well Limited | Health & social care | 2016 |
| LIZ Millington Interiors Limited | Administrative & support | 2006 |
| Lizdan Consultants Limited | Information & communication | 2006 |
| LJD Management Consultants Ltd | Administrative & support | 2021 |
| Llewelyn IT Communications Ltd | Information & communication | 2019 |
| Lmc-Architect Limited | Professional & scientific | 2013 |
| Lnnr Estates Ltd | Real estate | 2023 |
| Local 2 Global Consulting Ltd | Administrative & support | 2025 |
| London Student Conferences Limited | Extraterritorial | 2014 |
| Longley Bookkeeping and Accounting Services Ltd | Professional & scientific | 2024 |
| Looking Glass Consultancy Ltd | Information & communication | 2025 |
| Lorna Grey Designs Ltd | Professional & scientific | 2023 |
| Love Home Stays Ltd | Real estate | 2025 |
| Love Your Earth Ltd | Energy | 2020 |
| Loveday Accounting Ltd | Professional & scientific | 2018 |
| Lpcl Holding Company Limited | Financial services | 2022 |
| LSK Ventures Ltd | Real estate | 2025 |
| Lucent Marketing Ltd | Professional & scientific | 2025 |
| Lucky Hoof 2023 Ltd | Hospitality | 2023 |
| Lucy Lewin Ltd | Professional & scientific | 2020 |
| Lumynex Ltd | Information & communication | 2025 |
| LV Dryliners Ltd | Construction | 2026 |
| Lyddington Property Company Limited | Real estate | 2016 |
| Lyfe International Limited | Information & communication | 2025 |
| Lyndon Media Ltd | Information & communication | 2018 |
| Lyra Rose Retreats Limited | Hospitality | 2024 |
| M & a Calf Systems Limited | Wholesale & retail | 2020 |
| M & D Property Services Limited | Real estate | 2025 |
| M Baines Tiling Ltd | Construction | 2023 |
| M H Plastering Services Ltd | Construction | 2016 |
| M&H Pharma Limited | Wholesale & retail | 2011 |
| M&J Advisory Limited | Professional & scientific | 2017 |
| M.A. Tiling (Rutland) Limited | Construction | 2013 |
| M.Roberton Building Contractor Ltd | Construction | 2009 |
| Macconaill Services Limited | Health & social care | 2024 |
| Macduff Holdings Limited | Financial services | 2022 |
| Macfarlane Property Ltd | Real estate | 2021 |
| Macgregor Braavos Limited | Wholesale & retail | 2025 |
| Magic Scissorz Ltd | Other services | 2025 |
| Magnetomotive Ltd | Real estate | 2022 |
| Main Street (Seaton) Management Limited | Households | 2006 |
| Maison & Manor Limited | Real estate | 2024 |
| Maison SIX Limited | Wholesale & retail | 2025 |
| Major Oak Care Limited | Health & social care | 2023 |
| Mallorca Property Finder Limited | Real estate | 2017 |
| Mallspare Ltd | Professional & scientific | 2012 |
| Manderlay Properties Limited | Real estate | 2014 |
| Manor Farm Feeds (Owston) Limited | Manufacturing | 1998 |
| Manor Hill Management Company Limited | Households | 2001 |
| Manor Lane (Langham) Management Company Limited | Water & waste | 1998 |
| Marine Farm Aquatics Ltd | Agriculture & fishing | 2018 |