| Jarta Consulting Limited | Administrative & support | 2023 |
| JAX Windscreen Services Ltd | Wholesale & retail | 2025 |
| JAY Retail Ltd | Wholesale & retail | 2012 |
| Jayrick Records Ltd | Information & communication | 2020 |
| JC Air Conditioning Ltd | Energy | 2020 |
| JC Safety Consultancy Ltd | Professional & scientific | 2024 |
| JD Cook Recruitment Services Ltd | Administrative & support | 2026 |
| JD Hibbert Construction Limited | Construction | 2018 |
| JDB Detailing Ltd | Wholesale & retail | 2026 |
| Jeff Homes Ltd | Real estate | 2021 |
| Jeff Skips Limited | Water & waste | 2017 |
| Jell Amalgamation and Solutions Limited | Professional & scientific | 2017 |
| Jelt Creative Ltd | Professional & scientific | 2026 |
| JEM Safety Management Ltd | Professional & scientific | 1996 |
| Jemimapharma Limited | Professional & scientific | 2023 |
| Jemms Facilities Ltd | Professional & scientific | 2025 |
| Jess Carey Comms Ltd | Professional & scientific | 2025 |
| Jessica's Cafe Ltd | Hospitality | 2018 |
| Jfdiw Limited | Information & communication | 2011 |
| JG Services Herts Ltd | Construction | 2014 |
| JGB Electrical Limited | Administrative & support | 2019 |
| JHS Telecommunications Ltd | Information & communication | 2022 |
| Jigsaw Mortgages Limited | Financial services | 2007 |
| Jigsaw Mortgages Protection Ltd | Financial services | 2023 |
| Jihold (2025) Ltd | Professional & scientific | 2025 |
| Jims Sparks Limited | Construction | 2014 |
| JK Compliance Ltd | Professional & scientific | 2022 |
| JK Properties (London) Limited | Real estate | 2021 |
| JKM1 Limited | Real estate | 2018 |
| JLC Construction Limited | Construction | 2015 |
| JLF Group Ltd | Wholesale & retail | 2019 |
| JLP Event Support Ltd | Administrative & support | 2022 |
| JM2 Facilities Limited | Administrative & support | 2018 |
| JM2 Group Limited | Administrative & support | 2016 |
| JM2 Holdings Limited | Financial services | 2020 |
| JM2 Services Limited | Administrative & support | 2018 |
| JMD Fire and Security Consultants Ltd | Administrative & support | 2018 |
| Jmnb Consulting Limited | Professional & scientific | 2019 |
| JMR Construction Ltd | Construction | 2025 |
| John Trailer Services Limited | Manufacturing | 2008 |
| Johnson Crilly Solicitors LLP | | 2006 |
| Joint Ventures Property Ltd | Real estate | 2024 |
| JOL Group Limited | Construction | 2024 |
| Jolly Nose Ltd | Wholesale & retail | 2024 |
| Joseph Grace Estates Limited | Real estate | 2024 |
| Josh Jenner Limited | Education | 2018 |
| JP Apex Roofing Ltd | Construction | 2026 |
| JP Best Properties Ltd | Real estate | 2021 |
| Jpha Ltd | Wholesale & retail | 2019 |
| JPK Contracting Ltd | Construction | 2025 |
| Jpllj Limited | Professional & scientific | 2018 |
| JPT Management Ltd | Professional & scientific | 2025 |
| JR (Upminster) Limited | Wholesale & retail | 2026 |
| Jrdw Ltd | Construction | 2014 |
| JS7 Management Ltd | Professional & scientific | 2022 |
| JSA Global Limited | Transport & logistics | 2010 |
| JSD Consultancy Ltd | Administrative & support | 2018 |
| JT Consulting (Norfolk) Limited | Information & communication | 2011 |
| JT Drives & Patios Ltd | Administrative & support | 2026 |
| JT Moments Limited | Professional & scientific | 2025 |
| JTK Property Investments Limited | Real estate | 2026 |
| Jude Power Ltd | Manufacturing | 2023 |
| Juice HQ Ltd | Manufacturing | 2018 |
| Julian Paving Ltd | Construction | 2016 |
| Juliette Skincare & Beauty Ltd | Other services | 2026 |
| JWC Group Ltd | Wholesale & retail | 2016 |
| JWT Logistics Limited | Transport & logistics | 2022 |
| K B Design (Southern) Limited | Construction | 2012 |
| K Beauty Promotions Ltd | Other services | 2024 |
| K L Brickwork Ltd | Construction | 2015 |
| K Love Nail Limited | Other services | 2019 |
| K&F Capital Limited | Real estate | 2026 |
| Kairos Management Limited | Real estate | 2025 |
| Kairos Search Limited | Administrative & support | 2015 |
| Kala Estate Limited | Real estate | 2025 |
| KAM Wise Consultancy Ltd | Real estate | 2023 |
| Karlsburg AI Ltd | Information & communication | 2025 |
| Kate Reeves Consulting Ltd | Professional & scientific | 2025 |
| KAZ Executive Travel Ltd | Wholesale & retail | 2018 |
| KB & a Properties Ltd | Real estate | 2023 |
| KD Scala Ltd | Construction | 2022 |
| KDL Electrical Limited | Construction | 2015 |
| KEE Holmes Limited | Financial services | 2025 |
| Keefe Marketing Limited | Administrative & support | 2021 |
| Keely Kleen Limited | Administrative & support | 2014 |
| Kelkinis Ltd | Manufacturing | 2021 |
| Kellegher's Gym Ltd | Arts & recreation | 2026 |
| Kelleher Forwarding Ltd | Transport & logistics | 1988 |
| Keltco Limited | Professional & scientific | 2019 |
| KEN Rhodes Holdings Limited | Professional & scientific | 2019 |
| Kenbuck Trading Ltd | Wholesale & retail | 2025 |
| Kennedy Assistants Ltd | Administrative & support | 2023 |
| Kestrel Global Logistics Limited | Transport & logistics | 2008 |
| Kestrel Liner Agencies (Manchester) Limited | Transport & logistics | 2011 |
| Kestrel Liner Agencies Ltd. | Transport & logistics | 1994 |
| Kestrel Logistics Ltd | Financial services | 2024 |
| Kestrel Procurement Limited | Transport & logistics | 2011 |
| Key Services London Ltd | Extraterritorial | 2021 |
| KFG Services Ltd | Construction | 2023 |
| KGE Solutions Ltd | Information & communication | 2025 |