| Island Sweetshop Limited | Wholesale & retail | 2025 |
| Issh Estates Ltd | Real estate | 2021 |
| Issh Holdings Ltd | Financial services | 2020 |
| Itunu Ltd | Extraterritorial | 2021 |
| J & R Collective Ltd | Professional & scientific | 2025 |
| J&K Estate Management Ltd | Administrative & support | 2026 |
| J.D.Plumbing Limited | Construction | 2004 |
| J.P Waste Management Ltd | Water & waste | 2026 |
| Jacobs Barbers Bramley Ltd | Other services | 2024 |
| Jacobs Barbers Holdings Ltd | Financial services | 2024 |
| Jacobs Barbers Tadley Ltd | Other services | 2021 |
| James Colledge Consultancy Limited | Information & communication | 2007 |
| Jamie Stead Ltd | Real estate | 2026 |
| Jasmiah Ltd | Hospitality | 2020 |
| JB Roofing Services Southern Ltd | Construction | 2025 |
| JCB Consults 41 Ltd | Professional & scientific | 2021 |
| JCM Electrics Ltd | Construction | 2013 |
| JDT Drinks Company Ltd | Wholesale & retail | 2018 |
| Jejaro Ltd | Professional & scientific | 2023 |
| JJH Building Solutions ( Hampshire ) Ltd | Construction | 2023 |
| John Stacey Construction Limited | Construction | 1984 |
| Joshua Riley Apps & Development Ltd | Information & communication | 2021 |
| JRG Landscapes Ltd | Administrative & support | 2025 |
| JRK Services Ltd | Information & communication | 2024 |
| Jsnp Ltd | Professional & scientific | 2017 |
| Jubilee Computer Consultants Limited | Information & communication | 1997 |
| K P Brockbank Ltd | Construction | 2020 |
| K&T Networks Ltd | Information & communication | 2019 |
| Kalapos Business Services Limited | Professional & scientific | 2019 |
| Kameno Limited | Wholesale & retail | 2024 |
| Kate Ovens Ltd | Administrative & support | 2016 |
| KAY Will Property Ltd | Real estate | 2025 |
| Kayarose Ltd. | Wholesale & retail | 2017 |
| Kazuri London Limited | Manufacturing | 2012 |
| Keep IT Clean by Sean Ltd | Wholesale & retail | 2024 |
| Keep IT Wild CIC | Arts & recreation | 2020 |
| Kestrel Contracts Limited | Construction | 2019 |
| Key Seekers Ltd | Real estate | 2018 |
| Kijo Technologies Limited | Information & communication | 2017 |
| Kilrae Management Company Limited | Real estate | 2014 |
| King's Road Builders Ltd | Construction | 2008 |
| King's Road Renovations Ltd | Construction | 2016 |
| Kingfishers Construction Ltd | Construction | 2017 |
| Kingfishers Residents Management Company Limited | Households | 2005 |
| Kinit Limited | Information & communication | 2014 |
| KM Maintenance and Authoring Limited | Professional & scientific | 2025 |
| Kneller Human Capital Limited | Administrative & support | 2014 |
| Koala Enterprises Ltd | Wholesale & retail | 2022 |
| Kolba Ltd | Other services | 2020 |
| KPS Home Improvements Limited | Construction | 2010 |
| Kris With a K Creative Ltd | Information & communication | 2018 |
| KT Lettings and Developments Limited | Real estate | 2017 |
| KTP Development Ltd | Information & communication | 2018 |
| L & N Transport Ltd | Transport & logistics | 2015 |
| L & P Conversions Ltd | Construction | 2018 |
| L&H Services Limited | Professional & scientific | 2009 |
| Lagford Properties Ltd | Real estate | 2021 |
| Lambden LS Limited | Professional & scientific | 2012 |
| Lambe Meikle Medical Ltd | Health & social care | 2018 |
| Lamp and Ladder Ltd | Professional & scientific | 2021 |
| Lanes Contractors Ltd | Manufacturing | 2026 |
| Lanyardsonly Limited | Wholesale & retail | 2011 |
| Larchcopse Limited | Other services | 2019 |
| Latchmore-Alpette Limited | Real estate | 2016 |
| Lavender Electrical Services Ltd | Construction | 2005 |
| Layton Technical Services Ltd | Professional & scientific | 2019 |
| LB Aesthetics and Beauty Ltd | Other services | 2021 |
| LB Homes and Living Ltd | Households | 2023 |
| LB Prime Property Management Ltd | Households | 2024 |
| LB Property Groups Ltd | Real estate | 2023 |
| LB Property Sourcing Ltd | Real estate | 2023 |
| LDM Service Group Limited | Construction | 2026 |
| LE Flufy Ltd | Professional & scientific | 2024 |
| Leaderboard Golf Courses (Dale Hill) Limited | Professional & scientific | 2001 |
| Leaderboard Golf Courses (Oxfordshire) Limited | Professional & scientific | 2002 |
| Leading M&E Construction Ltd | Construction | 2021 |
| LEE Dental Care Ltd | Health & social care | 2009 |
| Level Aspirations Limited | Health & social care | 2023 |
| LG Cornerstone Property Care Ltd | Construction | 2026 |
| Liberty Design London Ltd | Professional & scientific | 2020 |
| Life Lofts Ltd | Construction | 2021 |
| Lifeist Ltd | Wholesale & retail | 2021 |
| Linkies World Ltd | Manufacturing | 2026 |
| Little Cherry Tots Ltd | Health & social care | 2024 |
| Little London Brides Limited | Wholesale & retail | 2018 |
| Little Stars PRE School Baughurst Ltd | Education | 2019 |
| LIX Property Ltd | Real estate | 2017 |
| Lmaxfitness Ltd | Education | 2024 |
| Loader Construction Ltd | Construction | 2023 |
| LOC-8 Homes Limited | Real estate | 2019 |
| London Construction Management Ltd | Professional & scientific | 2014 |
| London Street Property Ltd | Construction | 2018 |
| Love Your Style Ltd | Other services | 2007 |
| LS Tree & Garden Services Ltd | Administrative & support | 2025 |
| LT Legal Limited | Professional & scientific | 2015 |
| Lynfoye Limited | Professional & scientific | 2024 |
| Lynx Consultants Ssda Limited | Information & communication | 2014 |
| M P Hughes Plastering & Drylining Ltd | Construction | 2026 |
| M W Property Maintenance Limited | Other services | 2012 |
| M&E Properties Holdings Ltd | Real estate | 2025 |