| James & Co Accountants Limited | Professional & scientific | 2014 |
| James Grant (Farmers) Limited | Agriculture & fishing | 1973 |
| James Window Cleaning & Gutter VAC Limited | Administrative & support | 2022 |
| Jansons Country Boarding Limited | Agriculture & fishing | 2026 |
| Jaris Housing Limited | Real estate | 2025 |
| Jawku UK Ltd | Wholesale & retail | 2019 |
| Jaywood Limited | Information & communication | 2025 |
| JB Motorsport Ltd | Administrative & support | 2025 |
| JB Trans 70 Ltd | Transport & logistics | 2020 |
| Jbka Consulting Ltd | Information & communication | 2022 |
| JC Builders Lincs Ltd | Construction | 2026 |
| JC Consultancy Limited | Construction | 2006 |
| JCH Services (Boston) Ltd | Construction | 2022 |
| JCS Driveways Limited | Construction | 2017 |
| JD Moto Service Limited | Wholesale & retail | 2025 |
| JD Rose Electrical Limited | Construction | 2019 |
| Jdarail UK Limited | Construction | 2012 |
| JDB Property Services Ltd | Construction | 2023 |
| JDG Creative Limited | Information & communication | 2019 |
| Jdww Limited | Health & social care | 2025 |
| Jeaatraders Limited | Wholesale & retail | 2026 |
| JEB Housing Ltd | Real estate | 2026 |
| Jeff Royle Limited | Agriculture & fishing | 2007 |
| Jessops Bakery Limited | Wholesale & retail | 2002 |
| JF Windscreen Repair Ltd | Wholesale & retail | 2022 |
| JGS Cleaning Limited | Administrative & support | 2025 |
| Jiff Logistics Ltd | Transport & logistics | 2017 |
| JK Burch Construction Ltd | Construction | 2013 |
| JLE Logistics Limited | Extraterritorial | 2017 |
| Jliral Ltd | Wholesale & retail | 2020 |
| Jlts Group Ltd | Hospitality | 2025 |
| JM Car Sales U.K. Limited | Wholesale & retail | 2015 |
| JMB Logistics Ltd | Transport & logistics | 2026 |
| JNF Transport Ltd | Transport & logistics | 2021 |
| Jobik UK Limited | Health & social care | 2011 |
| Jobquest Connect Ltd | Administrative & support | 2025 |
| Jobs Done Property Maintenance Ltd | Construction | 2021 |
| Jobtrac+ Ltd | Information & communication | 2015 |
| John a Knight Limited | Professional & scientific | 2007 |
| John Bark Plumbing & Heating Limited | Construction | 2011 |
| John Grant (Donington) | Agriculture & fishing | 1987 |
| John Neal Farms (Sibsey) Limited | Agriculture & fishing | 1982 |
| John Richardson & SON (Gosberton) Limited | Agriculture & fishing | 1955 |
| John Saul (Holdings) Limited | Financial services | 2016 |
| John Saul Limited | Agriculture & fishing | 1989 |
| Jordan Wrisdale Limited | Arts & recreation | 2026 |
| Josh Productions Limited | Information & communication | 2017 |
| Joven Limited | Construction | 2007 |
| JP & DJ Limited | Hospitality | 2014 |
| JP Asset Consulting Ltd | Professional & scientific | 2024 |
| JP Asset Sourcing & Management Ltd | Real estate | 2024 |
| JP Capital Holdings Ltd | Real estate | 2024 |
| JP Motor Group Ltd | Wholesale & retail | 2021 |
| JPS Bodyworks Ltd | Wholesale & retail | 2017 |
| JR Motion Ltd | Wholesale & retail | 2026 |
| JRK Real Estates Limited | Real estate | 2017 |
| Jsasl Ltd | Administrative & support | 2020 |
| JSP Leisure (East Midlands) Limited | Hospitality | 2023 |
| JSS Consultants Limited | Professional & scientific | 2007 |
| JSW Ecom Ltd | Wholesale & retail | 2024 |
| JTS Services Ltd | Construction | 2026 |
| Jubilee Buildings (Peterborough) Limited | Real estate | 2005 |
| Julara Ltd | Other services | 2026 |
| Julidaka Ltd | Transport & logistics | 2025 |
| Junktion Antiques Limited | Wholesale & retail | 2007 |
| Jurassic Encounters Ltd | Arts & recreation | 2015 |
| Jurciks Limited | Transport & logistics | 2019 |
| Jurela Ltd | Wholesale & retail | 2023 |
| Just Carping Ltd | Wholesale & retail | 2014 |
| Just SIX Limited | Real estate | 2015 |
| Jventa Limited | Transport & logistics | 2026 |
| JWK Contractors Ltd | Agriculture & fishing | 2017 |
| Jwrh Properties Limited | Real estate | 2023 |
| K &L Catering Food Truck Ltd | Hospitality | 2024 |
| K&D Horizons Ltd | Real estate | 2026 |
| K&K Growers Ltd | Wholesale & retail | 2024 |
| K&M Landscaping Limited | Administrative & support | 2026 |
| K-Bam Limited | Health & social care | 2023 |
| K-Develo Limited | Real estate | 2020 |
| K.H. Marshall (Electrical Contractors) Limited | Construction | 1975 |
| K.K.S. Sweets Ltd | Hospitality | 2025 |
| K.N. Grant Limited | Agriculture & fishing | 1985 |
| KA Leisure (Boston) Limited | Hospitality | 2021 |
| KA Services & Inspections Limited | Transport & logistics | 2012 |
| Kaizen Engineering Services Ltd | Professional & scientific | 2025 |
| Kalas Packaging Limited | Manufacturing | 2009 |
| Kalas Properties Limited | Real estate | 2015 |
| Kalev Group Ltd | Construction | 2019 |
| Kalingana Limited | Real estate | 2026 |
| Kamelita Limited | Transport & logistics | 2019 |
| Kammak Ltd | Transport & logistics | 2019 |
| Kandy Homes & Healthcare Ltd | Real estate | 2016 |
| Kandy Medical Services Limited | Health & social care | 2019 |
| Karolina External Transport Management Ltd | Transport & logistics | 2025 |
| Karolina Transport Limited | Transport & logistics | 2016 |
| Karp Trans Ltd | Transport & logistics | 2026 |
| Kass & Co. Lettings Ltd | Real estate | 2025 |
| Kast Art Studio Ltd | Arts & recreation | 2024 |
| Katmandu Limited | Wholesale & retail | 2014 |
| Kaunas Wings Limited | Transport & logistics | 2015 |