| K Estates (NE) Limited | Real estate | 2017 |
| K Hatfield Lingerie Ltd | Wholesale & retail | 2013 |
| K Lawson Ltd | Wholesale & retail | 2024 |
| K R Pubs Limited | Hospitality | 2024 |
| K S Darlo Ltd | Real estate | 2020 |
| K&Ahomesuk Limited | Real estate | 2018 |
| K.C.L North East Ltd | Wholesale & retail | 2019 |
| K.H.Orthopaedic Limited | Professional & scientific | 2024 |
| K8OS Leadership & Coaching Ltd | Education | 2016 |
| K9 House of Style Ltd | Administrative & support | 2016 |
| K9 Kennels Ltd | Wholesale & retail | 2023 |
| Kaelen Limited | Wholesale & retail | 2026 |
| Kalantzis Limited | Professional & scientific | 2018 |
| Kane's World Ltd | Education | 2025 |
| KAP Accounting Services Limited | Professional & scientific | 2016 |
| Karak Chaii Middlesbrough Ltd | Hospitality | 2023 |
| Karhel Limited | Professional & scientific | 2011 |
| Karma Thai Massage Ltd | Health & social care | 2023 |
| Kart Marketplace Ltd | Wholesale & retail | 2023 |
| Karting Promotions Ltd | Arts & recreation | 2017 |
| Kasher Properties Limited | Real estate | 2022 |
| Kasmidesigns Ltd | Manufacturing | 2023 |
| Kataleya Logistics Ltd | Transport & logistics | 2020 |
| Katbert Supplies Ltd | Extraterritorial | 2017 |
| Kate Fraser Gowns Limited | Wholesale & retail | 2019 |
| Kate Heslop Limited | Health & social care | 2018 |
| Kate Morris Aesthetics Ltd | Health & social care | 2025 |
| Katerina Victoria PMU & Aesthetics Ltd | Other services | 2023 |
| Katie Douglas Limited | Information & communication | 2006 |
| Kavana Ltd | Arts & recreation | 2021 |
| Kaznorm Ltd | Construction | 2019 |
| KB Van Sales Ltd | Wholesale & retail | 2025 |
| Kbiz Limited | Hospitality | 2022 |
| KBV Publishing Ltd | Extraterritorial | 2024 |
| KC3D Ltd | Wholesale & retail | 2024 |
| KCV Constructions Ltd | Construction | 2024 |
| KD Cuisine Limited | Hospitality | 2021 |
| Kearney Roofing & Sons Limited | Construction | 2025 |
| Kebab Grill Bondgate Ltd | Hospitality | 2025 |
| Keel & Green Caterers Ltd | Hospitality | 2024 |
| Keenest Property Ltd | Real estate | 2025 |
| Kelly’S Kitchen and Desserts Ltd | Hospitality | 2025 |
| Keloran Limited | Information & communication | 2025 |
| Kemitra for Digital Marketing Ltd | Administrative & support | 2025 |
| Kenmore Plastics Ltd | Manufacturing | 2023 |
| Kensington Windows & Conservatories Ltd | Manufacturing | 2001 |
| Kent Properties North East Ltd | Real estate | 2024 |
| Kerforo Ltd | Professional & scientific | 2026 |
| Kerry Louise Limited | Wholesale & retail | 2025 |
| KES Design Ltd | Construction | 2024 |
| Kestrel Kitchen Installations Ltd | Construction | 2022 |
| Kettler UK Ltd | Construction | 2022 |
| Kevdelivery Ltd | Transport & logistics | 2026 |
| Kevin Peter Bryson Limited | Extraterritorial | 2025 |
| Key 2 Moving on Limited | Hospitality | 2017 |
| Key 4 Moving on Limited | Health & social care | 2023 |
| Key 4 Services Limited | Construction | 2024 |
| Key Fitness Studio Limited | Other services | 2016 |
| Key Interiors Limited | Construction | 2015 |
| Key Legal (North East) Limited | Professional & scientific | 2013 |
| Key Minister Ltd | Wholesale & retail | 2016 |
| Keystone Architectural Surveying and Developments Limited | Construction | 2024 |
| Khan Rooms Ltd | Hospitality | 2023 |
| Khaza Kustoms Ltd | Wholesale & retail | 2023 |
| Khepri Holdings Ltd | Financial services | 2024 |
| Khondokar Group Limited | Financial services | 2023 |
| Khondokar Holdings Limited | Financial services | 2026 |
| KHS Scaffolding Contractors Limited | Construction | 2026 |
| Kickstart Hosting Ltd | Extraterritorial | 2025 |
| Kiddies Corner Nursery Limited | Education | 2002 |
| Kids FUN Klub Ltd | Education | 2023 |
| Kidsons Leeds Limited | Other services | 2009 |
| Kiecom Limited | Information & communication | 2013 |
| Kielder Water Club Limited | Education | 1983 |
| Kinbuilder Consultancy Limited | Professional & scientific | 2016 |
| King Cole Mills Management Company Limited | Households | 2006 |
| King Hope Ltd | Professional & scientific | 2014 |
| King's Broadcasting Services Limited | Information & communication | 2019 |
| Kingfisher Gardening Services Limited | Administrative & support | 2017 |
| Kingfisher Logistics Ltd | Transport & logistics | 2025 |
| Kingfisher Projects Limited | Professional & scientific | 2025 |
| Kingston Teal Limited | Professional & scientific | 2016 |
| Kingsway Planning Ltd | Professional & scientific | 2017 |
| Kingswell Recruitment Private Limited | Health & social care | 2020 |
| Kinnie&Co Ltd | Real estate | 2019 |
| Kinship Developments Ltd | Real estate | 2025 |
| KIP & Nook Limited | Hospitality | 2020 |
| Kipling Accountants Limited | Professional & scientific | 2014 |
| Kirby 754 Engineering Ltd | Professional & scientific | 2026 |
| Kirkstall Investment Ltd | Wholesale & retail | 2023 |
| Kitchen Brigade Ltd | Administrative & support | 2020 |
| KJA Trading Limited | Other services | 2018 |
| KJM Investment Properties PTY Ltd | Real estate | 2020 |
| KKE Properties Ltd | Real estate | 2019 |
| KKF Holdings Ltd | Financial services | 2015 |
| Klarient Limited | Information & communication | 2006 |
| Kleek Education Limited | Extraterritorial | 2022 |
| Klemens Transport Limited | Transport & logistics | 2014 |
| Klobberkng Ltd | Wholesale & retail | 2025 |
| KLS Darlington Ltd | Other services | 2024 |