| JPJ Installations Limited | Manufacturing | 1997 |
| JPS Brickwork Limited | Construction | 2015 |
| JR Mot's Limited | Wholesale & retail | 2023 |
| JRC Developments Limited | Construction | 2019 |
| Jrms Group Limited | Manufacturing | 2020 |
| JRS Automotive Ltd | Manufacturing | 2016 |
| JRS Plumbing & Heating Services Ltd | Construction | 2019 |
| Jrvdevi Company Limited | Hospitality | 2018 |
| JS Enterprise (Essex) Ltd | Hospitality | 2011 |
| JSF Building Contractors Ltd | Construction | 2018 |
| JSM Vehicle Services Ltd | Wholesale & retail | 2009 |
| JT4 Developments Ltd | Construction | 2022 |
| Judith Lawrence Presents Ltd | Administrative & support | 2015 |
| Juggel Ltd | Wholesale & retail | 2026 |
| Juggle Energy Limited | Information & communication | 2023 |
| Juggle Holdco Limited | Financial services | 2023 |
| Juice Developments Limited | Construction | 2015 |
| Juij Holdings Ltd | Real estate | 2025 |
| Julie Bennett Commerce Ltd | Extraterritorial | 2025 |
| Juma Estates Services Ltd | Financial services | 2025 |
| Juniorlayer Limited | Wholesale & retail | 2026 |
| Juniper and Hare Ltd | Wholesale & retail | 2023 |
| Juss TAG Limited | Other services | 2021 |
| Just Booze Limited | Hospitality | 2025 |
| Just Content Ltd | Other services | 2013 |
| Just Like Jennings Limited | Arts & recreation | 2005 |
| JV Electrical Essex Limited | Construction | 2025 |
| JW Electrics (Essex) Limited | Construction | 2013 |
| JW Moore Utilities Ltd | Energy | 2025 |
| Jwbp Limited | Real estate | 2023 |
| JWC Catering Ltd | Hospitality | 2022 |
| JWC Lettings Ltd. | Real estate | 2016 |
| JWC20 Limited | Professional & scientific | 2024 |
| Jwood Investments Ltd | Real estate | 2020 |
| JWS (G.B.) Limited | Wholesale & retail | 2005 |
| K & D Starie Limited | Construction | 2014 |
| K & G Social Limited | Other services | 2025 |
| K E C Engineering Limited | Manufacturing | 2010 |
| K Fleming Financial Limited | Professional & scientific | 2019 |
| K M R Haulage Limited | Transport & logistics | 2001 |
| K O Optimal Health Ltd | Other services | 2019 |
| K&S Mens Room Limited | Other services | 2002 |
| K.K Witham Station Comfort Cabs Ltd | Transport & logistics | 2022 |
| K2 Drylining Ltd | Construction | 2020 |
| K9 Coach Dog Training Ltd | Other services | 2022 |
| Kabernik & Sons Ltd | Wholesale & retail | 2020 |
| Kady Investments Limited | Real estate | 2016 |
| Kafften Limited | Construction | 2009 |
| Kajed Ltd | Information & communication | 2024 |
| Kalestead Holdings Limited | Real estate | 2002 |
| Kalestead Limited | Manufacturing | 1980 |
| Kamzin Health Consultancy Ltd. | Health & social care | 2017 |
| Karen Till Limited | Professional & scientific | 2006 |
| Karl Bunting Services Limited | Construction | 2020 |
| Karmatica Ltd | Construction | 2013 |
| Karoma Limited | Wholesale & retail | 2022 |
| Kash Global Consultants Ltd | Wholesale & retail | 2025 |
| Kayli Accounts Ltd | Professional & scientific | 2019 |
| Kayvilin Property Holdings Ltd | Real estate | 2025 |
| KB Sales Consultancy Ltd | Real estate | 2023 |
| Kblm Investments Limited | Real estate | 2025 |
| KBR Lettings Ltd | Real estate | 2025 |
| KCA Planning Ltd | Professional & scientific | 2022 |
| Kccs Group Ltd | Administrative & support | 2026 |
| KDB Office Services Ltd | Agriculture & fishing | 2021 |
| KDI Interiors Ltd | Construction | 2020 |
| Keeldean Limited | Wholesale & retail | 1978 |
| Keenmount Dagenham Services Limited | Administrative & support | 1998 |
| Keith Flint Music Limited | Arts & recreation | 2021 |
| Keith Rice & SON Limited | Construction | 2003 |
| Kelly Waste Ltd | Water & waste | 2025 |
| Kenrith 303 Ltd | Wholesale & retail | 2026 |
| Kent Clan Investments Ltd | Real estate | 2023 |
| Kent Investments Group Limited | Real estate | 2021 |
| Kevin Kirby Limited | Wholesale & retail | 1999 |
| Kevin Pollard Limited | Information & communication | 2018 |
| Key Auto Sales Limited | Wholesale & retail | 2021 |
| Keys Investments Limited | Hospitality | 2002 |
| Keystone Plumbing Contractors Limited | Construction | 2020 |
| Khan Food Ltd | Hospitality | 2024 |
| Khassenova IT Ltd | Information & communication | 2017 |
| KHC Freehold Limited | Real estate | 2006 |
| Khitservices Ltd | Information & communication | 2025 |
| Kiki's Aromas Ltd | Wholesale & retail | 2025 |
| Kiki’S Munchies Limited | Hospitality | 2025 |
| Kimberly Ogan Online Coaching Ltd | Other services | 2024 |
| KIN Catering Limited | Hospitality | 2019 |
| Kina Group Limited | Professional & scientific | 2018 |
| King Arthur Training Ltd | Other services | 2026 |
| King Loft Conversions Limited | Construction | 2018 |
| Kingfisher Drainage and Jetting Ltd | Water & waste | 2021 |
| Kings Accountancy Services Limited | Professional & scientific | 2020 |
| Kings Financial Ltd | Extraterritorial | 2008 |
| Kings of Clerkenwell Limited | Other services | 2015 |
| Kings Property Consultants Limited | Real estate | 2013 |
| Kings Retreats Ltd | Hospitality | 2024 |
| Kingswood (UK) Limited | Extraterritorial | 1998 |
| Kingwell Holdings Limited | Agriculture & fishing | 1995 |
| Kirby & Co Ltd | Arts & recreation | 2005 |
| Kirsty Hawkes Mckenzie Friend Ltd | Administrative & support | 2021 |