| Jumbosupply Ltd | Wholesale & retail | 2021 |
| Jumis Cake Studio Ltd | Manufacturing | 2025 |
| Juniper Energy Limited | Energy | 2024 |
| Juris North Legal Limited | Professional & scientific | 2026 |
| Just Cargo IT Limited | Transport & logistics | 2025 |
| Just Hard Metals Ltd | Construction | 2015 |
| Just in Time Couriers North East Ltd | Transport & logistics | 2025 |
| Just Insurance Agents Limited | Financial services | 2005 |
| Just LET Your Soul Grow CIC | Education | 2016 |
| Just R (UK) Ltd | Construction | 2005 |
| Just Rewardz Ltd | Wholesale & retail | 2024 |
| Just Travel Solutions Limited | Extraterritorial | 2014 |
| Justtravelcover.Com Limited | Extraterritorial | 2014 |
| JVJ Property Ltd | Households | 2020 |
| JVM Europe Limited | Wholesale & retail | 2010 |
| JW Electrical Group Ltd | Construction | 2022 |
| JW Properties North East Limited | Real estate | 2025 |
| JWS Site Solutions Ltd | Construction | 2019 |
| K and D Business Services Limited | Hospitality | 2018 |
| K Armstrong Design Limited | Administrative & support | 2017 |
| K Bleasdale Motors Ltd | Wholesale & retail | 2017 |
| K D Kassim Renewables Ltd | Construction | 2019 |
| K M Snowdon Building and Joinery Limited | Administrative & support | 1995 |
| K Sirmond Property Ltd | Real estate | 2024 |
| K-Mech Heavy Equipment Limited | Wholesale & retail | 2023 |
| K. HO and Co. Limited | Professional & scientific | 1996 |
| K.O Coatings and Inspection Ltd | Professional & scientific | 2013 |
| K.W. GAS Services Ltd | Construction | 2013 |
| Kaare Ltd | Wholesale & retail | 2020 |
| Kafinix Ventures Ltd | Wholesale & retail | 2025 |
| Kaft Property Limited | Real estate | 2023 |
| Kaila Investments Ltd | Real estate | 2023 |
| Kairos Point Consultancy Ltd | Information & communication | 2025 |
| Kaito Events Ltd | Professional & scientific | 2020 |
| KAL (NE) Limited | Construction | 2023 |
| Kalamis Limited | Professional & scientific | 2023 |
| Kalanikethan Indian Arts, Music and Sports Centre C.I.C. | Education | 2023 |
| Kaleido Leisure Limited | Hospitality | 2024 |
| Kaleido Leisure Newcastle Ltd | Hospitality | 2025 |
| KAM Asbestos Solutions Ltd | Water & waste | 2026 |
| Kameron 19 Ltd | Wholesale & retail | 2019 |
| Kamran's Barber Sunderland Limited | Other services | 2017 |
| Kans and Kandy (Holdings) Ltd | Professional & scientific | 2006 |
| Kans and Kandy (Propco Holdings) Ltd | Extraterritorial | 2022 |
| Kans and Kandy (Properties) Ltd | Real estate | 2006 |
| Kans and Kandy (Property) Ltd | Extraterritorial | 2022 |
| Kans and Kandy (Renewables) Ltd | Extraterritorial | 2022 |
| Kans and Kandy (Wholesale Holdings) Ltd | Extraterritorial | 2022 |
| Kans and Kandy (Wholesale) Ltd | Wholesale & retail | 2000 |
| Kanto Box Ltd | Hospitality | 2026 |
| Kanvoz Direct Ltd | Wholesale & retail | 2023 |
| Kanyakumari Investments Ltd | Real estate | 2020 |
| Kanyan (NE) Ltd | Hospitality | 2024 |
| Kaplans Turkish Barber Ltd | Other services | 2016 |
| Karekind Healthcare Ltd | Administrative & support | 2026 |
| Karls Property Services Ltd | Real estate | 2026 |
| Karnaphuli Limited | Administrative & support | 2011 |
| Karol Property Company Limited | Real estate | 1986 |
| Karrick Solutions Ltd | Wholesale & retail | 2025 |
| KARSOFT2022 Ltd | Construction | 2025 |
| Karveen Ltd | Hospitality | 2025 |
| Kata Accounting Solutions Ltd | Professional & scientific | 2021 |
| Kathryn Tatton and Oliver Tatton Limited | Real estate | 2017 |
| Katie Bulmer Cooke Limited | Arts & recreation | 2013 |
| Katie V Photography Ltd | Professional & scientific | 2024 |
| Katie Ward Homes Ltd | Construction | 2025 |
| Kavish Retail Ltd | Wholesale & retail | 2022 |
| Kaylen’S Property Ltd | Real estate | 2020 |
| KB Fibre Services Ltd | Construction | 2025 |
| KB Specialist Access Ltd | Professional & scientific | 2024 |
| KB Wind Services Ltd | Manufacturing | 2022 |
| Kb's Launderette Ltd | Other services | 2025 |
| KC Production Consultant Ltd | Manufacturing | 2020 |
| KC Property Management UK Limited | Other services | 2005 |
| KCT Engineering Ltd | Professional & scientific | 2025 |
| KDL Properties NE Ltd | Real estate | 2026 |
| KDM Cranes and Lifting Ltd | Professional & scientific | 2025 |
| KDO Investco Limited | Financial services | 2024 |
| KE Rope Access Ltd | Construction | 2025 |
| KE Tucky Ltd | Real estate | 2020 |
| Kean Media Limited | Professional & scientific | 2011 |
| Kebab House South Hetton Ltd | Hospitality | 2025 |
| KED Developments Limited | Extraterritorial | 2017 |
| Keelman Construction Ltd | Construction | 2008 |
| Keep Active (NE) C.I.C. | Administrative & support | 2011 |
| Keerthi Ltd | Wholesale & retail | 2024 |
| Keerthisainadh Limited | Wholesale & retail | 2025 |
| Keey Solutions Limited | Construction | 2019 |
| Keith Hodson Racing Limited | Arts & recreation | 2010 |
| Keith's Services Ltd | Wholesale & retail | 2025 |
| Kelf Electrics Ltd | Construction | 2017 |
| Kelly & Duggan Home Improvements Ltd | Construction | 2025 |
| Kelvin House Ltd | Real estate | 2022 |
| Kembol Limited | Health & social care | 2023 |
| Kenect (North East) Limited | Administrative & support | 2021 |
| Kenfolk Ltd | Professional & scientific | 2020 |
| Kengen Limited | Financial services | 2023 |
| Kenian Logistics Ltd | Information & communication | 1964 |
| Kennek Construction Limited | Manufacturing | 2001 |
| Kerckhoffs Ltd | Information & communication | 2017 |