| Jeanette Haley Limited | Information & communication | 2012 |
| JEN Halliwell Consulting Limited | Professional & scientific | 2012 |
| Jerrys Joinery UK Limited | Construction | 2008 |
| Jessica Harris PR Limited | Professional & scientific | 2021 |
| JF Consulting & Business Services Limited | Construction | 2022 |
| JHT Consulting Limited | Information & communication | 2018 |
| Jigsaw Land Limited | Real estate | 2013 |
| Jiver Ltd | Other services | 2019 |
| JJ Integrated Solutions Limited | Administrative & support | 2006 |
| JM Group of Companies Ltd | Financial services | 2018 |
| Jmont Consultancy Limited | Administrative & support | 2022 |
| JNR Reservoir Engineering Ltd | Professional & scientific | 2015 |
| JOE Troedson Management Limited | Professional & scientific | 2015 |
| John Hillier Associates Limited | Professional & scientific | 2005 |
| Johnny Schnitzel Limited | Hospitality | 2021 |
| Johnson Consulting Limited | Financial services | 2018 |
| Johnson Young Limited | Financial services | 2015 |
| Joincraft Ltd | Professional & scientific | 2023 |
| Jolly Bees Gardening Ltd | Administrative & support | 2024 |
| Jolly Pets Ltd | Extraterritorial | 2021 |
| Jolt Digital Limited | Professional & scientific | 2021 |
| JON LUC Industries Ltd | Wholesale & retail | 2023 |
| Jones & Jones Solutions Ltd | Professional & scientific | 2017 |
| Jordan Frank Limited | Professional & scientific | 1999 |
| Jordan Shaw Music Limited | Arts & recreation | 2023 |
| Jordi Devas Associates Limited | Information & communication | 2010 |
| Josie COX Media Limited | Information & communication | 2019 |
| JP Burgess Holdings Ltd | Financial services | 2025 |
| JP Interior Consulting Ltd | Construction | 2025 |
| JP Interior Services Ltd | Construction | 2020 |
| JR Divine Group Ltd | Wholesale & retail | 2026 |
| JRM Systems Consultancy Limited | Information & communication | 2014 |
| JS Global Engineering Ltd | Professional & scientific | 2020 |
| JS Massage Therapy Ltd | Health & social care | 2021 |
| Jsoms Ltd | Professional & scientific | 2023 |
| JSS (London Residential) Limited | Real estate | 2007 |
| JSS Mayfair Limited | Extraterritorial | 2011 |
| Jtonic Ltd | Information & communication | 2014 |
| JTP Lighting Ltd | Information & communication | 2013 |
| Julia Jones Media Ltd | Information & communication | 2014 |
| Julie Godefroy Sustainability Ltd | Professional & scientific | 2016 |
| Jumpcut Films Ltd | Information & communication | 2012 |
| Junction Catalyst Limited | Information & communication | 2023 |
| Junction LDN Limited | Administrative & support | 2018 |
| Jungle Mind Limited | Professional & scientific | 2008 |
| JVZ Limited | Information & communication | 2024 |
| K & K Moves Limited | Water & waste | 2020 |
| K & S General Services Ltd | Construction | 2010 |
| K&A Home Solutions Ltd | Construction | 2025 |
| K&K UK Construction Ltd | Construction | 2011 |
| K-Min Limited | Wholesale & retail | 2025 |
| KAH HOU Ltd | Wholesale & retail | 2022 |
| Kaizen Advisory & Management LLP | | 2025 |
| Kaizen Kaikan LLP | | 2024 |
| Kalafat Rose Limited | Professional & scientific | 2009 |
| Kalmly Ltd | Information & communication | 2025 |
| Kapil Mehek Enterprises Limited | Real estate | 2017 |
| Kardia Digital Ltd | Information & communication | 2024 |
| Kash & Devi Limited | Wholesale & retail | 2024 |
| Kate Feather Kitchen Design Ltd | Manufacturing | 2016 |
| Katey's House Limited | Education | 2010 |
| KBC Special Events Limited | Arts & recreation | 2003 |
| KC Residents Association Limited | Households | 1991 |
| KCF Management Consulting Ltd | Professional & scientific | 2016 |
| KCP Assets (NO.2) Limited | Real estate | 2024 |
| KCP Assets Limited | Real estate | 2024 |
| KE Ventures Ltd | Professional & scientific | 2023 |
| Keatons Group Limited | Real estate | 1995 |
| Keith Boyfield Associates Limited | Professional & scientific | 2011 |
| Kelly VFX Limited | Information & communication | 2016 |
| Kemlegal Limited | Professional & scientific | 2023 |
| Kennington Lane Properties Ltd | Extraterritorial | 2024 |
| Kevin Barry Stonemasonary Ltd | Construction | 2007 |
| Key to Music London Ltd | Administrative & support | 2017 |
| Kharis Consulting Ltd. | Construction | 2023 |
| Kharis Holdings Ltd | Construction | 2024 |
| KHG International Real Estate UK Ltd | Financial services | 2020 |
| KI Films Ltd | Information & communication | 2016 |
| Kiin Tech Limited | Information & communication | 2022 |
| Kima Limited | Professional & scientific | 2000 |
| Kindred Systems OS Ltd | Information & communication | 2024 |
| Kingfisher Court Freehold Company Limited | Households | 2001 |
| Kings Road Management Company Limited | Households | 1985 |
| Kingsdale Properties Limited | Real estate | 1953 |
| Kingsley Gratrick Productions Ltd | Administrative & support | 2018 |
| Kingston & Teddington Osteopathy Limited | Extraterritorial | 2003 |
| Kingston Close Limited | Households | 1998 |
| Kingswood Lodge Company Limited | Professional & scientific | 2006 |
| Kinly Care Group Limited | Real estate | 2017 |
| Kioni Talent Limited | Administrative & support | 2023 |
| Kipling Drive (Merton) Management Company Limited | Households | 1986 |
| Kirby Jones Management Limited | Professional & scientific | 2014 |
| Kiro Investment Group Ltd | Real estate | 2021 |
| Kirsten Reid Creative Ltd | Professional & scientific | 2024 |
| Kiru Ltd | Manufacturing | 2026 |
| KL Teddington Limited | Households | 2026 |
| Kmbpg Group Limited | Wholesale & retail | 2026 |
| KMW Developments Brighton FH Ltd | Construction | 2021 |
| KMW Developments Limited | Construction | 2016 |
| Knightsbridge House RTM Company Limited | Households | 2025 |