| Jbai Holdings Limited | Real estate | 2023 |
| JC Wine Associates Ltd | Education | 2021 |
| Jeff Skidmore Agricultural Limited | Administrative & support | 2010 |
| JJS Building Contractors Ltd | Construction | 2023 |
| JL Management Ltd | Real estate | 2023 |
| Jodecoba Limited | Construction | 2018 |
| John D Kilby & Co Limited | Professional & scientific | 2003 |
| John D Kilby Developments Limited | Real estate | 2007 |
| Johnheart Ltd | Construction | 2022 |
| Joyce & Joan Limited | Wholesale & retail | 2020 |
| JT Marketing PR Limited | Information & communication | 2011 |
| JT Marketing Services Limited | Extraterritorial | 2011 |
| Juri Properties Ltd | Real estate | 2017 |
| JWG Projects Limited | Administrative & support | 2025 |
| K N R Sign Installations Limited | Construction | 2006 |
| Kanbi Group Limited | Extraterritorial | 2009 |
| Kashec Limited | Professional & scientific | 1996 |
| Keegan Maze Ltd | Administrative & support | 2020 |
| Kelby Assets Ltd | Construction | 2024 |
| Kenilwade Limited | Hospitality | 1982 |
| Keystone Performance Partners Limited | Administrative & support | 2024 |
| KFG Lettings Ltd | Real estate | 2021 |
| KGC Contracts Ltd | Professional & scientific | 2007 |
| Killin IP Limited | Professional & scientific | 2014 |
| Kilogrammedia Limited | Professional & scientific | 2016 |
| Kimimila Ltd | Other services | 2025 |
| Kinetica Consult Ltd | Professional & scientific | 2014 |
| Kingdoms Corporate Horticulture Limited | Administrative & support | 2019 |
| Kingdoms Properties Limited | Real estate | 2025 |
| Klams Group Ltd | Energy | 2026 |
| Klear Coat Detailers Limited | Wholesale & retail | 2024 |
| Kodachrome Records Ltd | Information & communication | 2025 |
| Kose Restaurant Ltd | Hospitality | 2026 |
| Krowdrah Consulting Ltd | Education | 2014 |
| Kudu Travel Limited | Administrative & support | 1999 |
| Kwik Tyres & Auto Ltd | Wholesale & retail | 2024 |
| L D Knight Ltd | Agriculture & fishing | 2012 |
| L M Publishing Limited | Information & communication | 2010 |
| LA Law Legal Services Limited | Professional & scientific | 2013 |
| Lamps 2 U Direct Limited | Wholesale & retail | 2005 |
| Lamps Direct 2 U Limited | Wholesale & retail | 2005 |
| Landlord Cert Solutions Ltd | Households | 2025 |
| Larry KAY Electrical Limited | Administrative & support | 2017 |
| Laura Jeanne Limited | Wholesale & retail | 2026 |
| Lawrence James Property Ltd | Real estate | 2026 |
| Lawrence Lasers Ltd | Manufacturing | 2018 |
| Layston Preschool and Nursery CIC | Education | 2015 |
| LBT Computer Services Limited | Information & communication | 1992 |
| LCG Productions Limited | Professional & scientific | 2013 |
| LEA Valley Leasing Limited | Financial services | 2004 |
| Leecroft Brothers Ltd | Administrative & support | 2022 |
| Leeside Project Management Limited | Construction | 2018 |
| Let's Chat Ethics Ltd | Information & communication | 2021 |
| LHG Access Limited | Construction | 2003 |
| Light Illusion Limited | Information & communication | 2009 |
| Likeled UK Ltd | Wholesale & retail | 2026 |
| Little Coral Barn Ltd | Professional & scientific | 2025 |
| Little Gem's Pet Shop Ltd | Other services | 2018 |
| LJP Pest Control Services Limited | Administrative & support | 2018 |
| London Card Services Limited | Administrative & support | 2009 |
| London Steel Services (2024) Ltd | Manufacturing | 2024 |
| Louies Sandwich Bar of Buntingford Ltd | Hospitality | 2026 |
| LOVE4TRAVEL Ltd. | Administrative & support | 2016 |
| Luciano Photography Ltd | Professional & scientific | 2018 |
| Luminous London Ltd | Other services | 2019 |
| Luna Recruitment Ltd | Administrative & support | 2026 |
| Luxwood Bespoke Ltd | Wholesale & retail | 2021 |
| Lvlh Limited | Administrative & support | 2018 |
| M & F Gray Developments Limited | Construction | 1985 |
| M & H Electrical Solutions Limited | Construction | 2012 |
| M & M UK Retail Ltd | Wholesale & retail | 2015 |
| M D Watson Limited | Construction | 2003 |
| M F B Contract Flooring Limited | Construction | 2019 |
| M J Lampard Roofing Ltd | Construction | 2015 |
| M Rome Joinery Limited | Manufacturing | 2002 |
| M Star Ltd | Arts & recreation | 2023 |
| M-Rem Home Services Ltd | Manufacturing | 2026 |
| M.B.O. (Tools) Limited | Wholesale & retail | 2000 |
| M25 Hire Ltd | Administrative & support | 2025 |
| M7 Utilities Ltd | Energy | 2024 |
| Machrie Moor Trading Limited | Hospitality | 2026 |
| Mack Sales Ltd | Wholesale & retail | 2025 |
| Madsen Craig Limited | Information & communication | 2023 |
| Magic Mole Ltd | Wholesale & retail | 2024 |
| Manas Consulting Limited | Professional & scientific | 2012 |
| Maple Ridge Joinery Limited | Construction | 2013 |
| Mark Thomas Photography Limited | Administrative & support | 2003 |
| Markey Limited | Hospitality | 1998 |
| Marler Properties Limited | Real estate | 2021 |
| Marose Services Ltd | Health & social care | 2024 |
| Martins Plants Ltd | Agriculture & fishing | 2003 |
| Matt Walker Limited | Administrative & support | 2026 |
| Maxime Conatus Ltd | Information & communication | 2025 |
| MB Barbering Ltd | Other services | 2026 |
| MC Buntingford Ltd | Other services | 2024 |
| Mc-Jax Limited | Other services | 2019 |
| MC8 Limited | Professional & scientific | 2019 |
| Meadview Homes Ltd | Real estate | 2022 |
| Meister Vehicle Sales Limited | Wholesale & retail | 2026 |
| Melange Capital LP | | 2025 |