| Jonak UK Limited | Wholesale & retail | 2023 |
| Jonathan White Limited | Construction | 2004 |
| Jonomade Distilling Ltd | Manufacturing | 2018 |
| Josalo LLP | | 2024 |
| Joseph Isaac Hair Design Ltd | Other services | 2012 |
| Joseph Mccarthy Properties Limited | Construction | 2022 |
| Josh Mcmillan's Consultancy Vehicle Ltd | Information & communication | 2025 |
| Josh Rowell Limited | Arts & recreation | 2020 |
| Josiegrows Ltd | Administrative & support | 2025 |
| Jota Development Limited | Arts & recreation | 2013 |
| Jota Holdings Limited | Financial services | 2022 |
| Jota Limited | Extraterritorial | 2022 |
| Joust Digital Ltd | Professional & scientific | 2023 |
| JP Adams Builders Limited | Construction | 2005 |
| JP Group Holdings Ltd | Financial services | 2020 |
| JPC Systems Ltd | Information & communication | 2026 |
| Jpmrenovations Limited | Construction | 2025 |
| JR Invest LLP | | 2013 |
| JR Managing Ltd | Real estate | 2021 |
| JRE Marketing Ltd | Professional & scientific | 2026 |
| JRK Realisations Ltd | Other services | 2001 |
| JRR Wealth Services Limited | Financial services | 2016 |
| JRT Garran Consultants Limited | Information & communication | 2015 |
| JS Facilities Management Limited | Professional & scientific | 2018 |
| JS Playcentres Limited | Arts & recreation | 2008 |
| JSA Real Estate Limited | Real estate | 2021 |
| JSC Grabhire Ltd | Administrative & support | 2019 |
| JSC Management Ltd | Real estate | 2020 |
| JTA Design Limited | Professional & scientific | 2012 |
| JTA Trustees Limited | Administrative & support | 2022 |
| JTB Advisory Limited | Administrative & support | 2025 |
| JTE Holdings Ltd | Financial services | 2018 |
| JTP Developments Limited | Construction | 2021 |
| JTS Tennis Limited | Arts & recreation | 2016 |
| JTS Urban Design Ltd | Construction | 2025 |
| JTW Drafting Ltd | Professional & scientific | 2014 |
| Juan Stores Limited | Wholesale & retail | 2024 |
| Juicy Bike Limited | Wholesale & retail | 2008 |
| Julia Price Consulting Limited | Professional & scientific | 2023 |
| Julie Martin Limited | Professional & scientific | 2001 |
| Julie Reynolds Solicitor (UK) Limited | Administrative & support | 2009 |
| Julie Reynolds Solicitor LLP | | 2009 |
| Julien Garran Consultants LLP | | 2015 |
| Juliets Limited | Hospitality | 2010 |
| Juljo Limited | Administrative & support | 2012 |
| Jumbo Inns Ltd | Hospitality | 2022 |
| Jump IT Recruitment Solutions Limited | Administrative & support | 2002 |
| Jungle Guide Ltd | Education | 2012 |
| Junilu Holdings Ltd | Financial services | 2023 |
| Juniper Trades Limited | Real estate | 2018 |
| Juno Renewables Limited | Construction | 2025 |
| Jupiters Limited | Real estate | 1982 |
| Just BE Frank Driving School Limited | Education | 2025 |
| Just Celebrate Ltd | Hospitality | 2021 |
| Just Crystals Boutique Co Ltd | Administrative & support | 2014 |
| Just Posh Art Ltd | Wholesale & retail | 2009 |
| Just Quality Shoes. COM Limited | Wholesale & retail | 2019 |
| Just Roof Lanterns Limited | Administrative & support | 2015 |
| JUSTCLEAN7 Ltd | Administrative & support | 2025 |
| Justice Futures Community Interest Company | Professional & scientific | 2024 |
| Justin Quinn Ltd | Arts & recreation | 2012 |
| Justin Rippon Tea Procurement Consultancy Services Ltd | Professional & scientific | 2021 |
| JVN Property Ltd | Real estate | 2018 |
| JW Biodiversity Management Ltd | Professional & scientific | 2023 |
| JWC Plumbing Heating and Cooling Services Ltd | Construction | 2026 |
| Jweuk Ltd | Agriculture & fishing | 2023 |
| JWM Computing & Creative Limited | Information & communication | 2016 |
| JXG Management Solutions Limited | Professional & scientific | 2018 |
| K & L Stone Investments Limited | Real estate | 2021 |
| K & M Hogben Limited | Health & social care | 2012 |
| K B Tech Limited | Information & communication | 2005 |
| K Corp Ltd | Health & social care | 2025 |
| K F S (Crawley) Limited | Arts & recreation | 2017 |
| K J Saddles Limited | Wholesale & retail | 2019 |
| K L Invest LLP | | 2014 |
| K&K IT Consulting Limited | Information & communication | 2021 |
| K&R Media Ltd | Information & communication | 2015 |
| K. Davis & Co UK Limited | Wholesale & retail | 2005 |
| K. E. S. Cleaning Ltd | Construction | 2002 |
| K. J. Taylor (Haulage) Limited | Transport & logistics | 2007 |
| K.A.S Food Solutions Limited | Hospitality | 2020 |
| K.H.S. (Gravesend) Ltd | | 1977 |
| K9 Scruffy to Fluffy Dog Grooming Limited | Other services | 2015 |
| Kaaj Bedrooms & Kitchens Ltd | Manufacturing | 2016 |
| Kabir Search Ltd | Administrative & support | 2026 |
| Kaecoh Limited | Administrative & support | 2010 |
| Kaecoh Partners LLP | | 2023 |
| Kai's Family Limited | Hospitality | 2019 |
| Kairos Consulting Services Limited | Professional & scientific | 2015 |
| Kairos People Consulting Ltd | Administrative & support | 2024 |
| Kaliegh Dunn Ltd | Real estate | 2026 |
| Kall Kwik Sevenoaks Limited | Manufacturing | 2008 |
| Kalmax International Limited | Real estate | 2012 |
| Kamino-It Limited | Information & communication | 2013 |
| Kanasu Ltd | Real estate | 2017 |
| Kaner Olette Limited | Professional & scientific | 2008 |
| Kans Catering Ltd | Hospitality | 2021 |
| Kapital Property Developments Limited | Construction | 1997 |
| Kara Services Ltd | Construction | 2018 |
| Karaya Capital IV Limited | Financial services | 2023 |