| Kelio Limited | Information & communication | 2023 |
| Kelleher and Sons Ltd | Construction | 2022 |
| Kelliot Properties Limited | Real estate | 2021 |
| Kells Bay Kerry Limited | Construction | 2019 |
| Kelly Smith Ventures Limited | Professional & scientific | 2021 |
| Kelly's Caribbean Cuisine Ltd | Hospitality | 2022 |
| Kelly's Recycling Ltd | Water & waste | 2022 |
| Kelsey Management Holding Company Limited | Financial services | 2022 |
| Kelsey Management Investments Ltd | Administrative & support | 2022 |
| Kelsey Management Ltd | Information & communication | 2021 |
| Kembourne Consultants Limited | Information & communication | 1998 |
| Kemettech Ltd | Information & communication | 2024 |
| Kemma Consultancy Ltd | Professional & scientific | 2026 |
| Kempair Limited | Construction | 2003 |
| Kemsi Design Limited | Professional & scientific | 2019 |
| Kemsi Living Ltd | Professional & scientific | 2023 |
| Kendal Investments Limited | Other services | 2002 |
| Kendalside RTM Company Limited | Professional & scientific | 2010 |
| Kendid Food and Drinks Limited | Wholesale & retail | 2025 |
| Kenilworth Court (Watford) Limited | Households | 1959 |
| Kenmore Contractors Limited | Construction | 2002 |
| Kennard Ramsay Building Services Ltd | Construction | 2019 |
| Kennedy Town 21 Co., Ltd | Real estate | 2021 |
| Kensal Green Frames Limited | Construction | 1999 |
| Kenshel Services Limited | Information & communication | 2008 |
| Kensington Creations Ltd | Arts & recreation | 2021 |
| Kensington Mews Watford Limited | Households | 2003 |
| Kensington Tradesmen Limited | Construction | 2012 |
| Kensol Accountants Ltd | Professional & scientific | 2018 |
| Kent Property Alliance Limited | Real estate | 2016 |
| Kentcardio Ltd | Health & social care | 2016 |
| Kentford Residents Management Limited | Households | 1968 |
| Kenwood Court Limited | Households | 2012 |
| Kenwood Damp-Proofing Limited | Construction | 1982 |
| Kenzi Design Decorating Ltd | Construction | 2025 |
| Keoc Propco Limited | Financial services | 2021 |
| Keogh Electrical Limited | Construction | 2023 |
| KER Psychology Ltd | Education | 2023 |
| Keragrains Limited | Wholesale & retail | 2025 |
| Keratin.Kair Limited | Other services | 2024 |
| Kerferd Advisory Ltd | Professional & scientific | 2024 |
| Kernaja Construction Ltd | Construction | 2020 |
| Kernot Management Consultancy Ltd | Administrative & support | 2020 |
| Kernow Homes Limited | Real estate | 1981 |
| Kerola Online Limited | Information & communication | 2023 |
| Kerriwood Ltd | Real estate | 2022 |
| Kerville Properties Limited | Real estate | 2003 |
| Kesar Learning Exams and Revision Ltd | Administrative & support | 2024 |
| Kesar Learning Ltd | Education | 2023 |
| Kesara Property Limited | Real estate | 2025 |
| Kesavuk Ltd | Wholesale & retail | 2020 |
| Keston Premium Stays Ltd | Real estate | 2022 |
| Kestrel Court RTM Company Ltd | Households | 2014 |
| Kestrel Training and Consultancy Ltd | Professional & scientific | 2019 |
| Kets Creative Property Group Limited | Real estate | 2016 |
| Kettering Town FC 1872 Ltd | Financial services | 2024 |
| Kettles Holdings Limited | Financial services | 2019 |
| Kettles Limited | Construction | 1989 |
| Kevadiya Ltd | Other services | 2020 |
| Kevin Durkin Limited | Construction | 2009 |
| Kewal Investments Limited | Construction | 1978 |
| Key Engineering Limited | Financial services | 2021 |
| Key People Limited | Administrative & support | 1991 |
| Key Property (Herts) Ltd | Construction | 2018 |
| Key Travel Solutions Limited | Professional & scientific | 2019 |
| Keyadvisor Property Management Ltd | Real estate | 2024 |
| Keycept Ltd | Wholesale & retail | 2024 |
| Keye Consultancy Limited | Professional & scientific | 2014 |
| Keyhurst Limited | Information & communication | 2011 |
| Keypar Limited | Wholesale & retail | 2013 |
| KEYROOMS2STAY Ltd | Real estate | 2025 |
| Keys in Motion Ltd | Transport & logistics | 2023 |
| Keywell Property Solutions Limited | Real estate | 2025 |
| Kfitsc Limited | Professional & scientific | 2014 |
| KFR Design Ltd | Professional & scientific | 2023 |
| KG Superstore Ltd | Wholesale & retail | 2023 |
| KGK Genix (London) Limited | Manufacturing | 2013 |
| Kgni Property Ltd | Real estate | 2024 |
| KGS Wine Ltd | Wholesale & retail | 2025 |
| KH Freehold Ltd | Real estate | 1994 |
| KH Project Management Ltd | Construction | 2015 |
| KH Security Ltd | Administrative & support | 2018 |
| Khadijah Trading Ltd | Wholesale & retail | 2024 |
| Khalif Holding Group Ltd | Financial services | 2025 |
| Khan AJ Ltd | Construction | 2025 |
| Khan Baig Investments Ltd | Real estate | 2025 |
| Khan Vehicle Specialist Ltd | Wholesale & retail | 2023 |
| Khans Property Investments (PVT) Ltd | Real estate | 2025 |
| Khatam Alnabaeen Limited | Health & social care | 2013 |
| Khawaja & Shaan Limited | Real estate | 2019 |
| Khider Properties Limited | Real estate | 2025 |
| Khira Limited | Transport & logistics | 2015 |
| KHL Associates Limited | Professional & scientific | 2010 |
| Khloecare Limited | Health & social care | 2024 |
| KHM Leisure (Watford) Ltd | Extraterritorial | 2017 |
| Khnm Investments Limited | Financial services | 2023 |
| Khunduchi Ltd | Administrative & support | 2016 |
| KI BID Consulting Limited | Professional & scientific | 2025 |
| KI Dudley Ltd | Real estate | 2018 |
| Kiaa Properties Ltd | Real estate | 2017 |