| Juno Jaxxon Productions Ltd | Information & communication | 2025 |
| Jupiter Academics Limited | Education | 2025 |
| Jupiter Fincorp Limited | Information & communication | 2023 |
| Jupiter HR Solutions Limited | Information & communication | 2025 |
| Jupitor Investments Limited | Hospitality | 2014 |
| Jurfil Ltd | Administrative & support | 2020 |
| Jusam Services Limited | Health & social care | 2023 |
| Just a Hand of Help CIC | Health & social care | 2023 |
| Just Because Consulting Ltd | Administrative & support | 2012 |
| Just Comp & Bifold Doors Ltd | Wholesale & retail | 2020 |
| Just Fit IT Ltd | Construction | 2021 |
| Just George Limited | Information & communication | 2004 |
| Just LEE Ltd | Information & communication | 2015 |
| Just Nail-It Ltd | Construction | 2022 |
| Just One More Bike Ltd | Wholesale & retail | 2019 |
| Just Prestige Limited | Administrative & support | 2011 |
| Just Tops (MK) Limited | Manufacturing | 2007 |
| Just Vanilla Limited | Other services | 2011 |
| JUST4ENTERTAINMENT Limited | Arts & recreation | 2012 |
| Justchef Justin Limited | Hospitality | 2016 |
| Justcuz Ltd | Information & communication | 2023 |
| Justdan Cleaning and Valeting Ltd | Administrative & support | 2025 |
| Juste Logistics Limited | Transport & logistics | 2012 |
| Justman and Johnson Limited | Health & social care | 2019 |
| Justmdf Limited | Wholesale & retail | 2024 |
| Justplay Basketball UK C.I.C. | Arts & recreation | 2019 |
| Jusurep Services Ltd | Administrative & support | 2020 |
| Jutla Group Ltd | Real estate | 2026 |
| Juvian Services Ltd | Construction | 2026 |
| Juzwik Property Management Ltd | Real estate | 2024 |
| JVA Properties Ltd | Real estate | 2020 |
| Jvss Limited | Construction | 2026 |
| JW Consulting Associates Ltd | Professional & scientific | 2014 |
| JW Electrical Northampton Ltd | Construction | 2022 |
| JW Property Management Group Limited | Real estate | 2024 |
| JW Property Management Limited | Real estate | 2020 |
| JWC Performance Ltd | Arts & recreation | 2025 |
| Jwdks Food Ltd | Hospitality | 2018 |
| JWL Advisory (2025) Limited | Professional & scientific | 2022 |
| JWL Private Limited | Professional & scientific | 2013 |
| JWM Performance Ltd | Wholesale & retail | 2025 |
| Jworks Ltd | Information & communication | 2017 |
| JWP59 Ltd | Wholesale & retail | 2010 |
| JWR Performance Ltd | Arts & recreation | 2025 |
| JZ Accountancy Ltd | Professional & scientific | 2018 |
| JZ Modern Art Ltd | Arts & recreation | 2019 |
| K & Co. Holdings Limited | Transport & logistics | 2012 |
| K & D London Limited | Other services | 2017 |
| K & D Mini Market Limited | Wholesale & retail | 2017 |
| K & F Contracting Limited | Construction | 2004 |
| K & J Hird Limited | Administrative & support | 2003 |
| K & K Flower House Ltd | Wholesale & retail | 2022 |
| K & W Limited | Wholesale & retail | 1992 |
| K Alam Investments Limited | Real estate | 2025 |
| K and R Paving and Landscaping Ltd | Construction | 2020 |
| K Baird & SON Ltd | Construction | 2026 |
| K Broxholme & SON Ltd | Construction | 2007 |
| K Care Services Ltd | Public administration | 2025 |
| K Fast Food Ltd | Hospitality | 2022 |
| K FOX Limited | Professional & scientific | 2016 |
| K J Beasley Electrical Installations Limited | Construction | 2015 |
| K J Owen Plastering Ltd | Construction | 2002 |
| K KAY Cars Ltd | Transport & logistics | 2024 |
| K Mcmuldroch Limited | Professional & scientific | 2009 |
| K R Industries Limited | Households | 2020 |
| K S Property Interiors Ltd | Real estate | 2020 |
| K Stubbs Associates Ltd | Professional & scientific | 2004 |
| K W Marketing Ltd | Professional & scientific | 2020 |
| K Webb Consultancy Ltd | Professional & scientific | 2019 |
| K Whitehouse Consultancy Limited | Professional & scientific | 2014 |
| K Y (Northampton) Limited | Real estate | 2014 |
| K&E Toys Ltd | Information & communication | 2025 |
| K&K Dent Removal Ltd | Wholesale & retail | 2016 |
| K&K Global Estates Ltd | Real estate | 2022 |
| K&L Sayers Properties Ltd | Real estate | 2021 |
| K&M Carpentry and Building Services Limited | Construction | 2021 |
| K&O Security Ltd | Administrative & support | 2025 |
| K&P Property Services Ltd | Construction | 2025 |
| K-Jem Limited | Information & communication | 2006 |
| K-South Ltd | Transport & logistics | 2016 |
| K. P. Landscapers Ltd. | Administrative & support | 2015 |
| K. Ryan Consulting Limited | Professional & scientific | 2013 |
| K.B. Tyres (Wootton) Ltd. | Wholesale & retail | 2016 |
| K.C.V Transport Ltd | Transport & logistics | 2021 |
| K.I.M. Developments Limited | Construction | 1983 |
| K.J.&S Transport Ltd | Transport & logistics | 2014 |
| K.L.A.L. Properties Ltd | Hospitality | 2024 |
| K.M.Properties Limited | Administrative & support | 1955 |
| K.P Construct Services Ltd | Construction | 2022 |
| K.R. Court Limited | Households | 1991 |
| K.R. Fabrications and Installations Limited | Manufacturing | 2014 |
| K10 Breakdown Recovery Ltd | Transport & logistics | 2020 |
| K10 Properties Limited | Real estate | 2020 |
| K10 Recovery Ltd | Wholesale & retail | 2024 |
| K33 Services Ltd | Transport & logistics | 2023 |
| K4O5 Ltd | Information & communication | 2009 |
| K7 Holdings Limited | Hospitality | 2018 |
| K8 Solutions Ltd | Administrative & support | 2004 |
| K9 Electronics Ltd | Manufacturing | 2014 |
| K9 Security Protection Ltd | Administrative & support | 2019 |