| KEY4BUSINESS Limited | Professional & scientific | 2023 |
| Keyenable Limited | Professional & scientific | 2016 |
| Keythrough Limited | Professional & scientific | 2022 |
| Keyto Consulting Ltd | Professional & scientific | 2016 |
| Keyway Construction (S.E.) Ltd | Construction | 2015 |
| Keywest Management Limited | Administrative & support | 2005 |
| Keywire Limited | Information & communication | 2020 |
| KFP Limited | Real estate | 2023 |
| KG Mortgages Limited | Financial services | 2020 |
| KI Uber-Techie Ltd | Information & communication | 2014 |
| Ki-An (UK) Limited | Other services | 2005 |
| Kick Graphics Ltd | Professional & scientific | 2019 |
| KID of the Village Ltd | Professional & scientific | 2022 |
| Kiddo Club Ltd | Health & social care | 2024 |
| Kids Works (Soccer School) Limited | Arts & recreation | 2004 |
| Kieleris & Co Accounting Services Limited | Professional & scientific | 2014 |
| Kievits Ltd | Professional & scientific | 2003 |
| Kildare Advisors Ltd | Professional & scientific | 2025 |
| Kilfeather & Dumbrill Ltd | Wholesale & retail | 2005 |
| Kilnwood Associates Ltd | Administrative & support | 2017 |
| Kilnwood Construction Limited | Construction | 2025 |
| Kilnwood Property Maintenance Ltd | Construction | 2019 |
| Kimex Technology Limited | Professional & scientific | 1997 |
| Kinder Living CIC | Professional & scientific | 2020 |
| Kindred Human Factors Ltd | Professional & scientific | 2025 |
| Kinetic Innovations Limited | Manufacturing | 2007 |
| Kinetica Consulting Limited | Professional & scientific | 2009 |
| Kinetiq Life Sciences Ltd | Administrative & support | 2024 |
| King & Stevens (Plant & Tool Hire) Ltd | Construction | 1988 |
| Kingley Vale Limited | Professional & scientific | 2018 |
| Kings and Stevens Limited | Construction | 1973 |
| Kings Farm Property Limited | Real estate | 2023 |
| Kings Gate Horsham RTM Company Limited | Households | 2019 |
| Kingsfold Park Pumping Station Limited | Water & waste | 1996 |
| Kingslea James Talent Limited | Administrative & support | 2023 |
| Kingsley Creative Ltd | Information & communication | 2003 |
| Kingswood IT Consultancy Ltd | Information & communication | 2020 |
| Kinsbrook (Brooks Green) Management Company Ltd | Households | 2012 |
| Kinsbrook Vineyards Limited | Agriculture & fishing | 2018 |
| Kipu Ltd | Information & communication | 2013 |
| Kirsten Forensics Ltd | Information & communication | 2022 |
| Kishnubbly Ltd | Wholesale & retail | 2013 |
| Kismitt (Programme Management) Limited | Information & communication | 2020 |
| Kiteloop Capital Limited | Financial services | 2025 |
| Kiteloop Capital Partners LP | | 2025 |
| KJM Wealth Management Ltd | Financial services | 2012 |
| KKR Wine Ltd | Wholesale & retail | 2018 |
| Kleaners Ltd | Administrative & support | 1991 |
| Klocke Kitchens (U.K.) Limited | | 1979 |
| KM Aesthetics & Health Limited | Other services | 2025 |
| KM Elite Products Limited | Wholesale & retail | 2003 |
| KM Property Services (Southern) Ltd | Water & waste | 2024 |
| KMG Content Limited | Professional & scientific | 2015 |
| KMV Finance Ltd | Administrative & support | 2005 |
| Knepp Farms LLP | | 2018 |
| Knepp Swallows Ltd | Hospitality | 2022 |
| Knibbs Computer Services Ltd. | Information & communication | 1998 |
| Knightbridge Limited | Professional & scientific | 1996 |
| Knights of Sussex Limited | Administrative & support | 2019 |
| Know My Sheet Ltd | Information & communication | 2025 |
| Know Watt Electrical Ltd | Construction | 2024 |
| Knowtopia Ltd | Professional & scientific | 2005 |
| Knxion Ltd | Construction | 2020 |
| Koian (Mayfair) Limited | Construction | 2013 |
| Koian Limited | Financial services | 2012 |
| Komline-Sanderson Ltd | Water & waste | 1992 |
| Koppa Holdings Ltd | Financial services | 2024 |
| Korgi Consulting Services Ltd | Information & communication | 2020 |
| KP Equestrian LLP | | 2020 |
| KPA UK Limited | Wholesale & retail | 2008 |
| KPL Knowledge Solutions Ltd | Administrative & support | 2014 |
| KPM Investment Holdings Ltd | Construction | 2016 |
| KR Property Maintenance and Construction Ltd | Construction | 2020 |
| Kreon Architectural Lighting Ltd | Professional & scientific | 2013 |
| Krietech Ltd | Professional & scientific | 2017 |
| Krios Media Ltd | Professional & scientific | 2025 |
| KRW Bioreg Solutions Ltd | Professional & scientific | 2022 |
| KSL Developments (Faygate) Limited | Extraterritorial | 2017 |
| KSL Property Investment Ltd | Real estate | 2019 |
| Kulture Club Originals Ltd | Manufacturing | 2023 |
| Kurt Building Ltd | Construction | 2019 |
| Kwik Repairs Ltd | Other services | 2025 |
| Kyanite Limited | Information & communication | 2024 |
| Kynetix Financial Technology Limited | Information & communication | 2020 |
| Kynetix Technology Limited | Information & communication | 1996 |
| Kyoka Systems Ltd | Information & communication | 2025 |
| Kzar Limited | Wholesale & retail | 2018 |
| L & H Emmett Holdings Limited | Financial services | 2018 |
| L & MB Communications Ltd | Information & communication | 2014 |
| L a Cole Scaffolding Ltd | Construction | 2020 |
| L J K Consulting Ltd | Professional & scientific | 2018 |
| L S Training and Coaching Limited | Professional & scientific | 2014 |
| L&C Roofing & Building Ltd | Construction | 2024 |
| L&L Equestrian Ltd | Agriculture & fishing | 2024 |
| L. Laker Limited | Manufacturing | 1946 |
| L.J. Hebblethwaite Ltd | Administrative & support | 2001 |
| L.P. Harris Investments Limited | Financial services | 1961 |
| L.Smith Plant Hire Limited | Administrative & support | 2016 |
| L2B Trade Limited | Water & waste | 2024 |
| L2J Ltd | Financial services | 2020 |