| JON Mitchell Plastering Limited | Construction | 2018 |
| JON Sturgeon Hairdressing Ltd | Other services | 2003 |
| Jones & Co Interiors Ltd | Construction | 2025 |
| Jordan-Air Systems Limited | Manufacturing | 2011 |
| Josephine Coins Limited | Administrative & support | 2017 |
| Joshgpropertys Ltd | Real estate | 2026 |
| Jotmake Limited | Information & communication | 2022 |
| JP Solar Maintenance Ltd | Administrative & support | 2023 |
| JR Caddy Limited | Arts & recreation | 2023 |
| JRB Projects Limited | Construction | 2019 |
| JRS Total Services Limited | Construction | 2014 |
| JRW Property Group Ltd | Households | 2017 |
| JSJ Accountants Ltd | Professional & scientific | 2009 |
| Jsld Consultants Ltd | Construction | 2022 |
| JT Roofing and Building Services Ltd | Construction | 2026 |
| Jtef Consultancy Limited | Professional & scientific | 2025 |
| Junction Holdings Limited | Financial services | 2016 |
| Jungle Themes Ltd | Information & communication | 2024 |
| Jura Operations Limited | Real estate | 2015 |
| Just Another Mccracken's (JAM Bars) Limited | Hospitality | 2015 |
| Just DO IT Guides Limited | Information & communication | 2008 |
| Justin Klot Ltd | Wholesale & retail | 2019 |
| JV Maria Limited | Professional & scientific | 2015 |
| JVO Transport Ltd | Transport & logistics | 2025 |
| JWH Properties Ltd | Construction | 2020 |
| Jwtax Secretarial Ltd | Professional & scientific | 2025 |
| K and R Housing Ltd | Real estate | 2025 |
| K B Electrical Limited | Construction | 2002 |
| K Garden Ltd | Hospitality | 2024 |
| K K Mobile Tyre Service Limited | Wholesale & retail | 2007 |
| K M Commercials Ltd | Wholesale & retail | 2004 |
| K R Chandler Limited | Construction | 2013 |
| K R Roofing Specialists Ltd | Construction | 2009 |
| K W Glass (Braintree) Ltd | Construction | 2004 |
| K&H Foods Ltd | Hospitality | 2023 |
| Kabers Clarity Ltd | Information & communication | 2026 |
| Kaine Tours Limited | Administrative & support | 2015 |
| KAL Property Developments Ltd | Construction | 2015 |
| Kalonit Blossom Ltd | Health & social care | 2016 |
| Kalways Solutions Ltd | Health & social care | 2025 |
| Karl Farey Developments Limited | Construction | 2019 |
| Kartaway Limited | Extraterritorial | 2012 |
| Kasey Jane UK Ltd | Arts & recreation | 2021 |
| Kass 12 Ltd | Construction | 2023 |
| Kasten Services Limited | Construction | 1999 |
| Kate of Kensington Ltd | Administrative & support | 2023 |
| Kathomeed Ltd | Education | 2026 |
| Kavorin Limited | Administrative & support | 2026 |
| Kazzys Skincare Specialist Ltd | Other services | 2025 |
| KC Home Management Ltd | Hospitality | 2023 |
| KC10 Coaching Limited | Arts & recreation | 2025 |
| KDA Recruitment Limited | Administrative & support | 2012 |
| KDC Tech Ltd | Information & communication | 2026 |
| KDT Holdings Limited | Administrative & support | 2021 |
| KE London Consulting Limited | Financial services | 2015 |
| Kedro Ltd | Administrative & support | 2019 |
| Kedro Trades Ltd | Administrative & support | 2023 |
| Keeble Environment Services Ltd | Construction | 2017 |
| Keep on Kicking Music Limited | Administrative & support | 1997 |
| Kefim Limited | Households | 1963 |
| Keircon Solutions Limited | Information & communication | 2014 |
| Kelsey Kennelly RDH Ltd | Health & social care | 2016 |
| Kent Bray Counselling and Mentoring Ltd | Health & social care | 2024 |
| Kevendys Travel T/A Rayleigh Roadways Limited | Administrative & support | 1969 |
| Kevin Smith Autos Ltd | Wholesale & retail | 2022 |
| Kevin's Cabling Ltd | Construction | 2019 |
| Key Consilia Ltd | Professional & scientific | 2015 |
| Key Design Automotive Consultants Ltd | Administrative & support | 2010 |
| Key Dials Limited | Information & communication | 2023 |
| Keylock Games Ltd | Arts & recreation | 2021 |
| Keystone Bespoke Homes Ltd | Real estate | 2020 |
| Keyword Capital Ltd | Financial services | 2026 |
| KF Global Brands Limited | Other services | 2016 |
| KF Global Properties Ltd | Financial services | 2021 |
| Kidbusterz Limited | Health & social care | 2017 |
| Kids Club Ltd | Information & communication | 2025 |
| Kilbren Contracts Limited | Construction | 1988 |
| Kilcar Holdings Limited | Information & communication | 2015 |
| Kilfinichen Farms Limited | Financial services | 1989 |
| Kilfinichen Properties Limited | Real estate | 1963 |
| Killerwatts Holdings Ltd | Professional & scientific | 2023 |
| Kind Electrical Company Ltd | Construction | 2019 |
| Kings Upholstery of Hornchurch Limited | Wholesale & retail | 1998 |
| Kingscaping Ltd | Administrative & support | 2023 |
| Kingsley Secretaries Limited | Administrative & support | 2003 |
| Kingswood Property Rental Ltd | Real estate | 2021 |
| Kirbys Vehicle Refinishing Ltd | Wholesale & retail | 2024 |
| Kirkmuirhill Ltd | Administrative & support | 2008 |
| Kirkwood Extension Design & Planning Ltd | Professional & scientific | 2026 |
| Kirkwood the Extension Planning Company Ltd | Professional & scientific | 2023 |
| Kirwan and James Limited | Construction | 2015 |
| Kissing Gate Management Company Limited | Households | 2008 |
| Kitchencraft (Essex) Limited | Manufacturing | 2002 |
| Kitezest Limited | Extraterritorial | 2009 |
| Kjbakerenterprise Ltd | Hospitality | 2023 |
| KJP Consultancy Ltd | Professional & scientific | 2023 |
| Klaus Kalde Limited | Professional & scientific | 1999 |
| KLM Site Solutions Ltd | Administrative & support | 2023 |
| KLR Medi Spa Ltd | Health & social care | 2023 |
| KM Sealants Ltd | Construction | 2024 |