| JJB Building Contractors Limited | Construction | 2019 |
| JM Truck Parts Limited | Wholesale & retail | 2020 |
| Jmxp Ltd | Real estate | 2018 |
| JOE Huntley Detailing Ltd | Wholesale & retail | 2025 |
| Joembah Trusted Limited | Transport & logistics | 2018 |
| John Davis Photo Ltd | Administrative & support | 2011 |
| John Mower Group Ltd | Financial services | 2022 |
| John Pearmain Limited | Construction | 2002 |
| John Silver Holdings Limited | Wholesale & retail | 1974 |
| John Silver Limited | Wholesale & retail | 1938 |
| Jonathan Horwich Fine Art Limited | Professional & scientific | 2019 |
| Jonel Property Services Limited | Financial services | 2020 |
| Jongleurs Group Limited | Arts & recreation | 2020 |
| Josar Ltd | Wholesale & retail | 2024 |
| Joshua Electrical Limited | Construction | 2021 |
| Joyce Green Meadows (Phase 2) Flat Management Company Limited | Households | 1998 |
| JPD Autos Limited | Wholesale & retail | 2025 |
| JPS Welding & Fabrication Limited | Manufacturing | 2004 |
| JR Regen Consulting Ltd | Professional & scientific | 2023 |
| Jubilee Court (West Malling) Management Company Limited | Households | 2013 |
| Judipe Ltd | Other services | 2023 |
| Judnorth Flat Management Company Limited | Households | 1979 |
| Juniper and Maple House (Nightingale Park) Management Company Limited | Households | 2026 |
| Juniper Park HT06 (Berryfields, Aylesbury) Management Company Limited | Households | 2017 |
| Juno Store Ltd | Wholesale & retail | 2026 |
| JWC Holdings Ltd | Financial services | 2025 |
| JWC Innovations Ltd | Professional & scientific | 2025 |
| K Gibson Transport Limited | Transport & logistics | 1998 |
| K J Telecoms Limited | Information & communication | 2014 |
| K S Creates Limited | Professional & scientific | 2025 |
| K&M Investments Properties Ltd | Real estate | 2025 |
| K&S Property Ltd | Households | 2025 |
| K.D. Clark Limited | Wholesale & retail | 1996 |
| K1 Stars Ltd | Arts & recreation | 2018 |
| K3 Medics Ltd | Manufacturing | 2020 |
| Kalim BK Ltd | Information & communication | 2025 |
| Kaneda Locksmiths Ltd | Administrative & support | 2026 |
| Karbon Blue Ltd | Information & communication | 2023 |
| Karen Ashenden Design Limited | Professional & scientific | 2002 |
| Karen Preston Fashion Styling Limited | Manufacturing | 2019 |
| Karens Court (Enfield) Residents' Association Limited | Households | 1975 |
| Karma Technologies Limited | Information & communication | 2004 |
| Kassice Limited | Other services | 2013 |
| Kate Ogborn Productions Ltd | Information & communication | 2023 |
| Katy Ayling Interiors Ltd | Professional & scientific | 2024 |
| KB Umbrella Limited | Administrative & support | 2026 |
| KC Wood Floors Limited | Construction | 2026 |
| KD333 UK Ltd | Professional & scientific | 2022 |
| Keats Court Management Limited | Households | 2014 |
| Keeley Hire (Film and Television) Limited | Other services | 1974 |
| Keith IAN Limited | Real estate | 2003 |
| Kelly Court Management Limited | Households | 1986 |
| Kelmar Construction Ltd | Construction | 2005 |
| Kemisol Limited | Health & social care | 2009 |
| Kendal Gardens Management Company Limited | Professional & scientific | 2011 |
| Kendall Mechanical Services Ltd | Professional & scientific | 2021 |
| Kenita Holdings Limited | Real estate | 2021 |
| Kennett Heath Management Limited | Households | 2003 |
| Kensington Court NO.1 (Hendon) Management Company Limited | Households | 2005 |
| Kensington Gate Residents Management Company Limited | Households | 2026 |
| Kenton Packing Station Limited | Wholesale & retail | 1961 |
| Kenyon Block Consultants Limited | Administrative & support | 2003 |
| Kenyon Property Investments Limited | Real estate | 2016 |
| Kenzy Events Ltd | Professional & scientific | 2024 |
| Kevin Vaux Building Services Ltd | Construction | 2015 |
| KEW Riverside Park Residents Company Limited | Households | 2002 |
| Keyspacehomes Ltd | Real estate | 2020 |
| Keysten Limited | Other services | 1987 |
| Keystone Communications Ltd | Information & communication | 2004 |
| Kilcreene House RTM Company Limited | Households | 2011 |
| Kimble (Merton) Management Company Limited | Households | 1986 |
| Kinetic Residential Management Limited | Real estate | 2019 |
| Kingfisher Close Residents Association Limited | Real estate | 2007 |
| Kingfisher Heights Management Company Limited | Households | 2001 |
| Kingfisher Park Residents Management Company Limited | Households | 2014 |
| Kings Hundred Management Company (Bisley) Limited | Real estate | 2016 |
| Kings Quarter Apartments N1 Limited | Real estate | 2014 |
| Kingsbourne (Nantwich) Community Management Company Limited | Households | 2018 |
| Kingsdown Road Management Company Limited | Households | 2005 |
| Kingsgate Mews Management Company Limited | Households | 2007 |
| Kingsley Grange (Wickford) Residents Association Limited | Professional & scientific | 2003 |
| Kingsmere (Haslingden Road) Management Company Limited | Households | 2002 |
| Kingsway (Quedgeley) Management Company Limited | Households | 2006 |
| Kirby Physio Ltd | Health & social care | 2016 |
| Kitaineco Limited | Professional & scientific | 2024 |
| Kitchen 100 Ltd | Hospitality | 2025 |
| Kitchener Barracks Management Limited | Real estate | 2018 |
| KJC Commercial Contracts Ltd | Real estate | 2020 |
| KM IT Services Ltd | Information & communication | 2022 |
| KMG Construction Ltd | Construction | 2015 |
| Knights Elite Ltd | Construction | 2019 |
| Knights Keep Management Company Limited | Households | 2017 |
| Knightshayes Management Company Limited | Households | 2006 |
| Knoo Ltd | Information & communication | 2026 |
| Knowle House Freehold Company Ltd | Households | 2016 |
| Knowle House Management Co. Limited | Households | 1987 |
| KPD Cleaning Services Limited | Administrative & support | 2019 |
| Kreative Developments Ltd. | Construction | 2014 |
| Krisco-Trans Ltd | Transport & logistics | 2017 |
| KS Event Solutions Ltd | Administrative & support | 2022 |