| JJH Commercials Ltd | Extraterritorial | 2025 |
| JK Made Ltd | Wholesale & retail | 2025 |
| JLB Design Limited | Manufacturing | 2006 |
| Jlsa Ltd. | Professional & scientific | 2012 |
| JMB Bars Limited | Hospitality | 2015 |
| JMB Composites Limited | Manufacturing | 2016 |
| JMB Rose Welding Limited | Manufacturing | 2018 |
| JMH & MCL Properties Ltd | Real estate | 2018 |
| JMI Scaffolding (UK) Limited | Construction | 2017 |
| JMP Services (UK) Limited | Wholesale & retail | 2014 |
| JNS Support Services Limited | Administrative & support | 2010 |
| JO Flowers Wigs Ltd | Arts & recreation | 2021 |
| Joel Ryder Media Limited | Information & communication | 2012 |
| John Adams Leisure Limited | Wholesale & retail | 1983 |
| John Adams Trading Company Limited | Professional & scientific | 1967 |
| John Chapman Farms Limited | Agriculture & fishing | 1965 |
| John Crosland Limited | Professional & scientific | 2015 |
| John Price Consulting Ltd | Professional & scientific | 2024 |
| John Seymour Carpets Limited | Wholesale & retail | 2025 |
| John Webb Design Limited | Professional & scientific | 2003 |
| Johnnycocktail Limited | Professional & scientific | 2006 |
| Joint Financial Services Limited | Professional & scientific | 2018 |
| Jonathan Elphick Ltd | Financial services | 2024 |
| Jordan Audio Ltd | Information & communication | 2018 |
| Joyndar Limited | Manufacturing | 2019 |
| JP UK Solutions Limited | Professional & scientific | 2016 |
| JPT Design Consultants Ltd | Professional & scientific | 2015 |
| JPT Residential Limited | Real estate | 2023 |
| JRE Planning Ltd | Professional & scientific | 2022 |
| JRW Platinum Solutions Ltd | Construction | 2026 |
| JS Investigations Ltd | Administrative & support | 2015 |
| JS Trucking Limited | Transport & logistics | 2018 |
| Jshc Ltd. | Professional & scientific | 2016 |
| JSK Tippers Ltd | Transport & logistics | 2021 |
| Jsre Services Limited | Professional & scientific | 2013 |
| JST Brickwork Ltd | Construction | 2023 |
| JSW Electrotech Ltd | Professional & scientific | 2008 |
| JSX Healthcare Limited | Health & social care | 2015 |
| JTD Performance Limited | Wholesale & retail | 2025 |
| Jumma Kebab Ltd | Hospitality | 2025 |
| Jump Global Limited | Administrative & support | 2012 |
| Junk & Disorderly Limited | Wholesale & retail | 2020 |
| Just Digital Limited | Manufacturing | 2003 |
| Justdigitalsteve Ltd | Professional & scientific | 2019 |
| Justflight London Limited | Information & communication | 2015 |
| JVH Trade Ltd | Wholesale & retail | 2025 |
| JW Yards Limited | Real estate | 2025 |
| Jwminconsult Limited | Mining & quarrying | 2013 |
| K Cooper Motors Sawtry Limited | Wholesale & retail | 2024 |
| K M Asbestos Services Limited | Construction | 2025 |
| K Power Hire Ltd | Professional & scientific | 2019 |
| K Power Solutions Ltd | Professional & scientific | 2017 |
| K Sheldrake Building Services Limited | Administrative & support | 2011 |
| K4 Recruitment Ltd | Administrative & support | 2024 |
| KA Cleaning Services Ltd | Manufacturing | 2025 |
| KA Sweet Home Build Ltd | Construction | 2026 |
| Kaashini Limited | Real estate | 2024 |
| KAI CB Ltd | Hospitality | 2024 |
| Kairos Designs Ltd | Information & communication | 2017 |
| Kaizen Development Solutions Limited | Information & communication | 2009 |
| Kaizen Health and Performance Ltd | Health & social care | 2026 |
| Kaleela Designs Ltd | Manufacturing | 2025 |
| Kallierbelle Ltd | Transport & logistics | 2025 |
| Kamali Taxi Limited | Transport & logistics | 2019 |
| Kambar Limited | Real estate | 2002 |
| Kamminga Estates Ltd | Real estate | 2025 |
| Kanazawa Events Solutions Ltd | Administrative & support | 2016 |
| Kanazawa Judo Club Ltd | Arts & recreation | 2022 |
| Kanazawa Training Ltd | Administrative & support | 2014 |
| Kandy MAN Limited | Wholesale & retail | 2014 |
| Kanyugo Ltd | Other services | 2025 |
| Kapara London Limited | Wholesale & retail | 2015 |
| Karl Day Marine Limited | Construction | 2008 |
| Karve Solutions Limited | Administrative & support | 2022 |
| Kasa Catering Ltd | Hospitality | 2019 |
| Kashif Limited | Health & social care | 2025 |
| Kasia Zalewska Ltd | Financial services | 2016 |
| Kastom Koncept Apparel Ltd | Extraterritorial | 2024 |
| Katie Strange Recruitment Limited | Administrative & support | 2017 |
| Kaya Anderson Consultancy Ltd | Health & social care | 2013 |
| KD Cascades UK Limited | Wholesale & retail | 1996 |
| Kday Composites Ltd | Other services | 2014 |
| Kd’S Punjabi Kitchen Limited | Hospitality | 2025 |
| KEE Environmental Ltd | Water & waste | 2020 |
| Keeble Cottage Equestrian Centre Ltd | Agriculture & fishing | 2022 |
| Keeponrocking Limited | Transport & logistics | 2025 |
| Keirden Properties Limited | Real estate | 2017 |
| Kellard Estates Ltd | Real estate | 2019 |
| Keln Leas Management Company Limited | Real estate | 2002 |
| Kemm Properties Ltd | Real estate | 2018 |
| Kemp Garage Doors Limited | Administrative & support | 2001 |
| Kemp Property Investments Limited | Hospitality | 2016 |
| Kempshire Ltd | Transport & logistics | 2020 |
| Kempster Valves & Engineering Limited | Manufacturing | 2022 |
| KEN Booth & Co. Limited | Wholesale & retail | 1983 |
| Kendal FOX Properties Ltd | Real estate | 2025 |
| Kenneth Turner Homes Limited | Real estate | 2013 |
| Kentmere Cartons Holdings Limited | Financial services | 2025 |
| Kentmere Cartons Ltd | Manufacturing | 2020 |
| Kentmere Limited | Manufacturing | 1906 |