| JK Fountain Ltd | Hospitality | 2025 |
| JLN Consulting Ltd | Professional & scientific | 2024 |
| JM Family Law Limited | Professional & scientific | 2020 |
| JMH Regulatory Limited | Professional & scientific | 2024 |
| JMW Hammerhead Ltd | Administrative & support | 2017 |
| JO Ltd | Extraterritorial | 2022 |
| Joanna Wallis Handpainted Lamps Limited | Professional & scientific | 2003 |
| Jockey Club Estates Limited | Arts & recreation | 1968 |
| Jockey Club Farming Company Limited | Agriculture & fishing | 2012 |
| John Bakez Cakez Ltd | Wholesale & retail | 2025 |
| John Gosden Holdings Limited | Financial services | 2021 |
| John Turner Leisure Marketing Limited | Information & communication | 2010 |
| Johnson & Co Accountants Limited | Other services | 2002 |
| Johnson and Powell Building Services Limited | Construction | 2015 |
| Johnz Bakez and Eventz Ltd | Wholesale & retail | 2026 |
| Jolland Janes Ltd | Hospitality | 2026 |
| Jones Preclinical and Translational Consulting Limited | Professional & scientific | 2025 |
| Jonik Investments Limited | Real estate | 2022 |
| Jordan Builders (ELY) Ltd | Construction | 2003 |
| Joseph Parr Racing Ltd | Agriculture & fishing | 2019 |
| Josephine Harkins Designfuse Ltd | Professional & scientific | 2025 |
| JP Developments (Cambridge) Ltd | Construction | 2010 |
| JP Optix Ltd | Professional & scientific | 2013 |
| Jpsg UK Consultants Ltd | Professional & scientific | 2011 |
| JPT IT Services Limited | Information & communication | 2019 |
| JS Bloodstock Consultancy Ltd | Arts & recreation | 2017 |
| JS Fitness Camp Limited | Arts & recreation | 2014 |
| JSB & ALN Properties Ltd | Real estate | 2023 |
| JSL Strategy Ltd | Administrative & support | 2026 |
| JSO Property Services Ltd | Manufacturing | 2023 |
| JU Ltd | Extraterritorial | 2008 |
| Juddmonte Farms (East) Limited | Agriculture & fishing | 2000 |
| Juddmonte Farms Limited | Agriculture & fishing | 1983 |
| Juliette's Kitchen Limited | Hospitality | 2024 |
| Juliettebryant Limited | Hospitality | 2025 |
| July Ltd | Extraterritorial | 2021 |
| Junipa Limited | Real estate | 2002 |
| Just a Barber Ltd | Other services | 2026 |
| Just Blast and Paint Ltd | Manufacturing | 2023 |
| Just SO Plumbing Ltd | Construction | 2015 |
| Juster & Nickerson Ltd | Hospitality | 2024 |
| JW Flooring (East Anglia) Limited | Construction | 2026 |
| JWH Safety Consultancy Ltd | Professional & scientific | 2025 |
| K & Z Plumbing Ltd | Construction | 2021 |
| K Asby Consulting Limited | Other services | 2017 |
| K Hutchinson & SON Limited | Agriculture & fishing | 2021 |
| K J Hill Stud Limited | Extraterritorial | 2018 |
| K P Taxis (Newmarket) Limited | Transport & logistics | 2014 |
| K T O'Neill Limited | Arts & recreation | 2026 |
| K. Mcginty Roofing Limited | Construction | 2012 |
| K9 Digital Ltd | Information & communication | 2021 |
| KA Ltd | Extraterritorial | 2009 |
| Kabol Supermarket (UK) Ltd | Wholesale & retail | 2025 |
| Kabri Consulting Limited | Information & communication | 2023 |
| Kalbandi Limited | Real estate | 2017 |
| Kale Acquisitions Ltd | Real estate | 2021 |
| Kali Chronia Ltd | Health & social care | 2022 |
| Kamil Kodzik Transport Ltd. | Transport & logistics | 2013 |
| Karen Walmsley Associates Ltd | Education | 2016 |
| Kassel Auto's Ltd | Wholesale & retail | 2026 |
| Kassel Food Ltd | Wholesale & retail | 2025 |
| Kassel Ltd | Construction | 2025 |
| Katarch Limited | Professional & scientific | 2005 |
| Kaybee Catering Limited | Manufacturing | 2015 |
| KB Ltd | Extraterritorial | 2009 |
| KCS Kris Cleaning Services Ltd | Administrative & support | 2022 |
| Kelmart Limited | Manufacturing | 2014 |
| Kenmore Developments Ltd | Construction | 2025 |
| Kentford Automotive Ltd | Wholesale & retail | 1998 |
| Kentford Consulting Ltd | Professional & scientific | 2020 |
| Kentford Developments Limited | Construction | 1984 |
| Kentford Investments Limited | Administrative & support | 2005 |
| Kentford Property Services Limited | Real estate | 2025 |
| Kerri Radcliffe Bloodstock Limited | Arts & recreation | 2011 |
| Kesar Aikyam Group Limited | Real estate | 2023 |
| Keylocks Ltd. | Real estate | 2013 |
| Keystone Financials (Cambs) Limited | Professional & scientific | 2024 |
| KG NDT Limited | Professional & scientific | 2021 |
| KHK Racing Limited | Arts & recreation | 2020 |
| KHL Construction (NKT) Limited | Construction | 2018 |
| KI Ltd | Extraterritorial | 2009 |
| Kind Bloodstock Limited | Agriculture & fishing | 2021 |
| Kinder Arsh Ltd | Administrative & support | 2025 |
| Kiosk on the Green Limited | Hospitality | 2024 |
| Kirtling Construction and Design LLP | | 2005 |
| Kirtling Construction LLP | | 2008 |
| Kiviatech Ltd | Information & communication | 2026 |
| Klar Windows Limited | Manufacturing | 2019 |
| KM Security and Medical Ltd | Administrative & support | 2025 |
| KM Styling Ltd | Wholesale & retail | 2026 |
| KM Testing Ltd | Information & communication | 2025 |
| KMK Newmarket Ltd | Hospitality | 2018 |
| Kmtg Limited | Construction | 2013 |
| KN Ltd | Extraterritorial | 2009 |
| Knappett Roofing Limited | Construction | 2014 |
| KNF Pubs Ltd | Hospitality | 2016 |
| Knox Solutions Ltd | Professional & scientific | 2025 |
| KO Ltd | Extraterritorial | 2008 |
| KPF Bloodstock Limited | Arts & recreation | 2022 |
| KPF Racing Ltd | Arts & recreation | 2020 |