| Justdatathings Ltd | Professional & scientific | 2019 |
| Justice Defenders | Other services | 2007 |
| Justice Researcher UK Limited | Extraterritorial | 2002 |
| Justin Reid Ltd | Professional & scientific | 2025 |
| Justmartin Limited | Hospitality | 2020 |
| Jutt Foods Ltd | Other services | 2020 |
| Jvjones Ltd | Professional & scientific | 2025 |
| JVM Services Ltd | Manufacturing | 2025 |
| JVR Music Limited | Information & communication | 2025 |
| JVS Express Limited | Wholesale & retail | 2025 |
| JW Commercial Finance Ltd | Financial services | 2026 |
| JW Locks & Services Ltd | Construction | 2021 |
| JW Roadmarking Limited | Construction | 2019 |
| JWF Design Ltd | Professional & scientific | 2017 |
| JWG Nation Limited | Construction | 2012 |
| JWN Law Limited | Professional & scientific | 2021 |
| JWO Capital Limited | Financial services | 2017 |
| Jydeson UK Limited | Health & social care | 2021 |
| Jyoti Subs Ltd | Wholesale & retail | 2009 |
| JZJ Properties Ltd | Real estate | 2024 |
| K & M Roofing Solutions Ltd | Construction | 2020 |
| K & P Property Partners Limited | Real estate | 2024 |
| K & R Builders and Maintenance Ltd | Construction | 2025 |
| K & S Integrated Security Solutions Ltd | Administrative & support | 2025 |
| K a Construction Services Ltd | Construction | 2022 |
| K a Peri Peri Chicken Ltd | Hospitality | 2024 |
| K Ampusco Limited | Administrative & support | 2022 |
| K B K Consultancy Ltd | Professional & scientific | 2025 |
| K B Letting and Management Ltd | Real estate | 2025 |
| K Bishwokarma Limited | Health & social care | 2013 |
| K C K G Management Limited | Real estate | 2011 |
| K C Store Limited | Wholesale & retail | 2026 |
| K D Supermarket Limited | Wholesale & retail | 2014 |
| K Distribution Group Ltd | Wholesale & retail | 2026 |
| K Geddes Consulting Ltd | Professional & scientific | 2016 |
| K Ghuman Properties Limited | Real estate | 2021 |
| K J Capital Limited | Other services | 2021 |
| K Putman Ltd | Transport & logistics | 2024 |
| K R&D Ltd | Information & communication | 2015 |
| K S S (London) Limited | Real estate | 2017 |
| K V (Chester) Management Company Limited | Households | 2018 |
| K W Partners Limited | Information & communication | 2006 |
| K W Plumbing & Heating Ltd | Construction | 2025 |
| K&B Catering Ltd | Hospitality | 2026 |
| K&H Supplies Ltd | Wholesale & retail | 2024 |
| K&K Treasury Consulting Limited | Professional & scientific | 2018 |
| K&M Btls LLP | | 2023 |
| K&N @JJ Limited | Hospitality | 2023 |
| K&N Sparklebright Ltd | Administrative & support | 2025 |
| K&R Care Limited | Administrative & support | 2020 |
| K&S Convenience Limited | Wholesale & retail | 2011 |
| K&S Marketing Ltd | Other services | 2016 |
| K. a. Heritage Limited | Financial services | 2019 |
| K.D Crosdale (London) Ltd | Construction | 2024 |
| K.Greg Construction Ltd | Construction | 2017 |
| K.O. London Limited | Arts & recreation | 2000 |
| K.S Builders (UK) Ltd | Administrative & support | 2011 |
| K.Sons Property Maintenance & Renovation Ltd | Construction | 2024 |
| K2 Crisis & Resilience Limited | Professional & scientific | 2025 |
| K2 Scaffolding Solutions Ltd | Construction | 2025 |
| K3K Operations Ltd | Administrative & support | 2025 |
| KA & NA Properties Ltd | Real estate | 2019 |
| KA Johal Property Limited | Construction | 2025 |
| Kaac Properties Ltd | Real estate | 2023 |
| Kaana Klub Limited | Hospitality | 2026 |
| Kaat Properties Ltd | Real estate | 2014 |
| Kabano Ltd | Wholesale & retail | 2024 |
| Kabul Ice Cream Limited | Manufacturing | 2025 |
| Kaccy's Limited | Wholesale & retail | 2020 |
| Kacie Limited | Health & social care | 2008 |
| Kacper Express Ltd | Transport & logistics | 2016 |
| Kadace Limited | Other services | 2021 |
| Kadikleaning Ltd | Administrative & support | 2024 |
| Kadosh 9 Services Ltd | Administrative & support | 2024 |
| Kadosh Mikon Ltd | Wholesale & retail | 2025 |
| KAF Contractors Limited | Administrative & support | 2024 |
| Kahncrest Consulting Ltd | Real estate | 2024 |
| KAI Consulting Ltd | Administrative & support | 2020 |
| Kailasa (Kent) Ltd | Other services | 2025 |
| Kailasa Ltd | Other services | 2025 |
| Kailasa UK Micronation | Other services | 2020 |
| Kaimes Ltd | Information & communication | 2024 |
| Kainat Catering Services Ltd | Other services | 2022 |
| Kaine Place Estate Management Co Ltd | Real estate | 2007 |
| Kairos Flow Limited | Professional & scientific | 2025 |
| Kairosrealityhomes Ltd | Real estate | 2026 |
| Kakes Limited | Manufacturing | 2019 |
| KAL Holdings Limited | Real estate | 2019 |
| Kalaivanan Kandhasamy Ltd | Other services | 2020 |
| Kalams Services Limited | Education | 2022 |
| Kalan Construction Ltd | Construction | 2026 |
| Kalao Studios Ltd | Professional & scientific | 2022 |
| Kaleidoscope Services Limited | Other services | 2021 |
| Kalel Group Ltd | Real estate | 2022 |
| Kalel Motor Group Ltd | Wholesale & retail | 2025 |
| Kalico the Brand Ltd | Other services | 2024 |
| Kalina Consultancy Limited | Administrative & support | 2018 |
| Kalisco Ltd | Wholesale & retail | 2022 |
| Kalj&Tash Ltd | Administrative & support | 2025 |
| Kalloo Limited | Wholesale & retail | 2003 |