| JSJ24 Limited | Real estate | 2024 |
| Jslipps Limited | Administrative & support | 2014 |
| JTL Auto's Ltd | Wholesale & retail | 2024 |
| Jumpflex UK Limited | Wholesale & retail | 2017 |
| Junior Save Ltd | Financial services | 2019 |
| Jupiter Online Limited | Professional & scientific | 2003 |
| Jurrius Ltd | Real estate | 2025 |
| Just Cables & Accessories Ltd | Information & communication | 2017 |
| Juven Ltd | Professional & scientific | 2018 |
| Jwen Music Ltd | Education | 2025 |
| JX Capital Limited | Construction | 2013 |
| K&C (Coleherne) Limited | Real estate | 1993 |
| K&C (Newbury) Limited | Financial services | 2013 |
| K&C (Osprey) Limited | Households | 1984 |
| K&H Partners in Real Estate Ltd | Real estate | 2025 |
| K&W Cleaners Ltd | Administrative & support | 2025 |
| K&W Delivery Ltd | Transport & logistics | 2023 |
| K.A.R.O Invest Ltd | Real estate | 2023 |
| K.P. Hughes & Associates Ltd | Professional & scientific | 2017 |
| K.W. Homes Limited | Construction | 2008 |
| Kafro Ltd | Financial services | 2020 |
| Kagema Limited | Health & social care | 2022 |
| Kaija Ltd | Transport & logistics | 2016 |
| Kajal Decors Ltd | Wholesale & retail | 2024 |
| Kalipay Properties Ltd | Real estate | 2025 |
| Kalsa Ltd | Real estate | 2023 |
| Kami-Tec Ltd | Other services | 2023 |
| Kandy Consulting Ltd. | Professional & scientific | 2014 |
| KAO Prosperity Co Ltd | Hospitality | 2026 |
| Karina Overseas Investments Ltd | Professional & scientific | 2013 |
| Karki Property Ltd | Real estate | 2020 |
| Karma Property Group Ltd | Real estate | 2020 |
| Kashyap Global Export Ltd | Wholesale & retail | 2023 |
| Kaspers Invest Ltd | Real estate | 2025 |
| Kavia Solutions Limited | Information & communication | 2017 |
| Kaxa Trading Ltd | Hospitality | 2021 |
| KC Ecom Ltd | Professional & scientific | 2025 |
| KCO Living Ltd | Real estate | 2024 |
| KCR (Kite) Limited | Real estate | 1966 |
| KCR (Southampton) Limited | Real estate | 2018 |
| KCR Residential Reit PLC | Administrative & support | 2014 |
| KDL Pizzas Limited | Hospitality | 1997 |
| KED Corp Limited | Other services | 2024 |
| Kedbrooke Electricals Limited | Wholesale & retail | 2019 |
| Kelleher Property Services Limited | Real estate | 2019 |
| Kelvin Cooling Limited | Construction | 2013 |
| Kemp Estates Limited | Real estate | 2010 |
| Kempe Franzen Property Ltd | Real estate | 2026 |
| Kenley Care Home Holdings Limited | Professional & scientific | 2019 |
| Kenley Care Services Limited | Health & social care | 2019 |
| Kensington & Chelsea Roofing Ltd | Construction | 2024 |
| Kerhag Property Ltd | Real estate | 2024 |
| Kewticles Ltd | Other services | 2023 |
| Key Link Money (UK) Limited | Real estate | 2018 |
| KG Home Improvement Ltd | Construction | 2025 |
| Kidwai Property Holdings Ltd | Hospitality | 2025 |
| Kidwise Ltd | Education | 2023 |
| Kikilas (UK) Limited | Construction | 2014 |
| Kili Ltd | Wholesale & retail | 2026 |
| Kinect Recruitment Limited | Administrative & support | 2011 |
| Kinetik Trade Limited | Construction | 2023 |
| King Cars Limited | Wholesale & retail | 2016 |
| Kingsford Management Ltd | Administrative & support | 2019 |
| Kingsley & Ashcroft Ltd | Real estate | 2024 |
| Kingsley Print and Design Limited | Manufacturing | 1981 |
| Kingston Garden Services Limited | Extraterritorial | 2016 |
| Kingston Landscape Group Limited | Administrative & support | 2002 |
| Kingston Roofing Specialist Ltd | Construction | 2025 |
| Kingswood Professional Services Ltd | Professional & scientific | 2011 |
| Kinley Legal UK Limited | Professional & scientific | 2018 |
| Kiraly Properties Limited | Real estate | 2018 |
| Kiran Ghattaura Creative Ltd | Professional & scientific | 2024 |
| Kirsty Carden Ltd | Administrative & support | 2017 |
| Kishiman Ltd | Transport & logistics | 2017 |
| Kiss N Makeup Skin Care Limited | Other services | 2018 |
| Kitezh Limited | Financial services | 2021 |
| Kiveo Properties Ltd | Real estate | 2022 |
| Klager Limited | Other services | 2023 |
| KM Polymetal Trading Partnership LP | | 2013 |
| Kmsavingz Ltd | Information & communication | 2026 |
| KN Energy Solutions Limited | Energy | 2024 |
| Knidos Ventures Limited | Wholesale & retail | 2017 |
| Knight and Day Security Limited | Administrative & support | 2021 |
| Koncept Furnishing Ltd | Wholesale & retail | 2021 |
| Kozuni Investments Ltd | Real estate | 2023 |
| KP Roofing Services Ltd | Construction | 2023 |
| KPD Bgjt Limited | Financial services | 2017 |
| Krauss Ltd | Other services | 2023 |
| Krecer Properties UK Ltd | Real estate | 2020 |
| Kris Speed OK Ltd | Transport & logistics | 2018 |
| Kriss Air Conditioning Limited | Energy | 2023 |
| Krolik Spare Car Parts Limited | Wholesale & retail | 2011 |
| KRP Retailers Ltd | Wholesale & retail | 2025 |
| Krudo Consulting Ltd | Professional & scientific | 2025 |
| KSS 72 Limited | Information & communication | 2023 |
| Kuiper Housing Ltd | Real estate | 2022 |
| Kulla Exim Limited | Financial services | 2016 |
| Kura Solutions Limited | Information & communication | 2012 |
| KVL Local Store Ltd | Wholesale & retail | 2023 |
| KVN Electrical & Property Services Ltd | Construction | 2021 |