| JS Ground Maintenance Ltd | Administrative & support | 2024 |
| JS Manley Limited | Wholesale & retail | 2017 |
| JS Pubco Ltd | Hospitality | 2015 |
| JS Salestek Limited | Wholesale & retail | 2012 |
| JSD Plant Ltd | Wholesale & retail | 2024 |
| JSW Robotic Services Limited | Professional & scientific | 2008 |
| JT Commercial Consulting Limited | Professional & scientific | 2026 |
| JT Wholesale Solutions Ltd | Wholesale & retail | 2026 |
| JTB Studios Ltd | Education | 2020 |
| JTK Associates (Management) Limited | Professional & scientific | 2010 |
| JTK Associates LLP | | 2009 |
| JTL Heating and Bathrooms Ltd | Construction | 2019 |
| JTL Renovations Ltd | Construction | 2024 |
| Jukeboxjive UK Limited | Other services | 2017 |
| Juliarch Limited | Professional & scientific | 2011 |
| Jump Elite Coaching Limited | Education | 2025 |
| Jump Elite Sales Ltd | Administrative & support | 2017 |
| Jumpit Limited | Professional & scientific | 2015 |
| Junc Design & Communications Limited | Arts & recreation | 2000 |
| Jupiter (Chesham) Management Company Limited | Households | 2005 |
| JUS Fabrication Ltd | Professional & scientific | 2025 |
| Just 4 Mortgages (Newark) Limited | Financial services | 2002 |
| Just Beauty Direct Ltd | Administrative & support | 2014 |
| Just V YOU Ltd | Professional & scientific | 2026 |
| Just Vehicle Rental Limited | Administrative & support | 2013 |
| Just Vehicle Solutions Ltd | Extraterritorial | 2017 |
| JVS Plant Ltd | Administrative & support | 2024 |
| JW Erecting and Rigging Services Limited | Construction | 2019 |
| JWB Electrical Limited | Construction | 2025 |
| JWH Property Services Limited | Real estate | 2006 |
| K & L Transport Solutions Ltd | Transport & logistics | 2026 |
| K D F Electrical Limited | Construction | 2007 |
| K Martini Plastering Limited | Construction | 2020 |
| K Nicol Accounting Services Ltd | Professional & scientific | 2007 |
| K R Bayford Haulage Ltd | Transport & logistics | 2018 |
| K R Driveways Limited | Construction | 2022 |
| K S Constructionn Ltd | Construction | 2024 |
| K&D Cargo Ltd | Transport & logistics | 2026 |
| K&T Developments Limited | Construction | 2024 |
| K&W Interiors Limited | Financial services | 2025 |
| K'S Primes Properties Ltd | Real estate | 2024 |
| K.W.Richards Limited | Financial services | 1964 |
| K2W Properties Ltd | Real estate | 2020 |
| K4 Property Limited | Real estate | 2014 |
| KA Broughton Ltd | Construction | 2026 |
| Kaliber Construction Limited | Construction | 2006 |
| Kantlehner Limited | Real estate | 2016 |
| Kapitanczyk Limited | Transport & logistics | 2015 |
| Kapok (1988) Ltd | Manufacturing | 1988 |
| Karman Ltd | Real estate | 2007 |
| Kashandy Travel Limited | Administrative & support | 2014 |
| Kate Dixon Physiotherapy Ltd | Other services | 2023 |
| Kate Victoria Hair Limited | Other services | 2024 |
| Kats K9'S Ltd | Other services | 2026 |
| Kaya Partners Limited | Administrative & support | 2019 |
| Kazelia Limited | Wholesale & retail | 2025 |
| KBI Holdings Limited | Financial services | 2017 |
| KDP Trading Ltd | Wholesale & retail | 2016 |
| KDR Powerlines Limited | Construction | 2017 |
| KDS (Nottingham) Limited | Administrative & support | 2002 |
| Ke-Connect Internet Limited | Extraterritorial | 1997 |
| Ke-Connect Systems Limited | Extraterritorial | 1990 |
| Keconnect Group Limited | Extraterritorial | 1998 |
| Keconnect Maintenance Limited | Extraterritorial | 1995 |
| Kecw Services Limited | Construction | 2025 |
| Keel & Colley Limited | Financial services | 2023 |
| Keeling Perry Consulting Limited | Professional & scientific | 2025 |
| KEH Construction Limited | Construction | 2022 |
| Keith Sell Plumbing and Heating Engineers Limited | Construction | 2004 |
| Keld Ampworks Ltd | Manufacturing | 2025 |
| Kelham Filtration Services Ltd. | Professional & scientific | 2017 |
| Kellycare Newark Ltd | Health & social care | 2024 |
| Kelpharma Ltd | Wholesale & retail | 2015 |
| Kemp Medical Communications Ltd | Professional & scientific | 2018 |
| Kennysclassiccars Ltd | Wholesale & retail | 2024 |
| Kera Protein Ltd | Hospitality | 2023 |
| Kerry Cattle Association of the British Isles Ltd | Wholesale & retail | 2025 |
| Kestech Solutions Limited | Information & communication | 2000 |
| KEV & Albert Bars Limited | Hospitality | 2025 |
| KEV Jackson Ltd | Administrative & support | 2016 |
| Kev's Kitchen Limited | Hospitality | 2018 |
| Key Services (Bilsthorpe) Ltd | Manufacturing | 2019 |
| Keyhole Marine Limited | Education | 2024 |
| Keystone Advisers Ltd | Professional & scientific | 2025 |
| KG Investments Newark Ltd | Real estate | 2024 |
| KGE Property Ltd | Real estate | 2024 |
| Kinada Services Ltd | Health & social care | 2024 |
| Kindle Community Ltd | Health & social care | 2016 |
| Kinetic IT Services Limited | Information & communication | 2025 |
| Kingfisher Facilities Group Limited | Professional & scientific | 2000 |
| Kingfishers Management Company (1996) Limited | Households | 1996 |
| Kingz Karahi Ltd | Hospitality | 2024 |
| Kirby Homes Limited | Real estate | 2019 |
| Kirk and Bills Ltd | Construction | 2015 |
| Kirton Heatcare Ltd | Construction | 2021 |
| KJ Premium Ltd | Construction | 2023 |
| Kjag Trading Ltd | Wholesale & retail | 2026 |
| Kjlconsult Ltd | Information & communication | 2019 |
| KL Employment Law Limited | Professional & scientific | 2024 |
| Klva Services Ltd | Other services | 2025 |