| JK Carpentry Limited | Construction | 2020 |
| Jltelecom Ltd | Construction | 2025 |
| JM Garden Maintenance Services Ltd Ltd | Administrative & support | 2025 |
| JMP Furniture Solutions Limited | Manufacturing | 2014 |
| JMR Consulting Limited | Administrative & support | 1997 |
| JO Broadhead & Associates Limited | Professional & scientific | 2016 |
| Jobsortedpro Ltd | Information & communication | 2026 |
| Jodal Limited | Wholesale & retail | 1994 |
| John Mayhew & Associates Limited | Professional & scientific | 2026 |
| John the Turf Ltd | Administrative & support | 2021 |
| JON Alderton Ltd | Professional & scientific | 2014 |
| Journey Instruments UK Ltd | Wholesale & retail | 2024 |
| JRU Limited | Real estate | 2012 |
| JRW Enterprises Ltd | Wholesale & retail | 2008 |
| Js&T Limited | Hospitality | 2019 |
| JSK Proservices Ltd | Manufacturing | 2024 |
| Jspl (SP160) Ltd | Construction | 2021 |
| JT Security and Support Services Limited | Administrative & support | 2023 |
| JTA Group ( SE ) Ltd | Households | 2022 |
| JTY Limited | Real estate | 2010 |
| Jules Sturgess Automotive Ltd | Wholesale & retail | 2017 |
| Jurniq Ltd | Professional & scientific | 2025 |
| Just Place Limited | Hospitality | 2016 |
| JWF Services Limited | Wholesale & retail | 1990 |
| JWT Land Limited | Professional & scientific | 2018 |
| K-Link United Services Ltd | Wholesale & retail | 2026 |
| KA Property Maintenance Limited | Construction | 2022 |
| Kallu Ltd | Health & social care | 2019 |
| Kamotech Ltd | Manufacturing | 2016 |
| KBS Groundworks & Construction Ltd | Construction | 2020 |
| KD Nails Ltd | Other services | 2017 |
| Kedington Butchers Limited | Wholesale & retail | 2010 |
| Keil Maintenance Ltd | Construction | 2017 |
| Kennedy SMP Studio Ltd | Professional & scientific | 2026 |
| Keronite International Limited | Manufacturing | 2000 |
| Ketton Consultants Limited | Financial services | 2005 |
| Ketton Early Birds | Education | 2009 |
| Ketton Wealth Management Ltd | Financial services | 2011 |
| Key Mortgage Solutions Ltd | Professional & scientific | 2019 |
| KFT Transporte Ltd | Transport & logistics | 2018 |
| Kgmi Ltd | Wholesale & retail | 2018 |
| Kiiwii Clothing and Promotions Limited | Administrative & support | 2018 |
| Kimer Storage Solutions UK Limited | Wholesale & retail | 2011 |
| Kinisi Kinisi Limited | Professional & scientific | 2025 |
| Kinisi Leasing Limited | Professional & scientific | 2023 |
| KJH Consulting Services Limited | Other services | 2019 |
| KK Healthcare Solutions Ltd | Health & social care | 2026 |
| KL Household Services Ltd | Administrative & support | 2019 |
| Klura Labs Limited | Professional & scientific | 2024 |
| Klura Ltd | Professional & scientific | 2020 |
| Knightley Holidays Ltd | Administrative & support | 2019 |
| Koppert UK Limited | Professional & scientific | 1981 |
| Krans Ltd | Professional & scientific | 2010 |
| KRM Car-Tech Ltd | Wholesale & retail | 2026 |
| Kusiara Limited | Hospitality | 2023 |
| L D Energy Solutions Limited | Construction | 2012 |
| L J Carpentry (UK) Limited | Construction | 2016 |
| L Nowak Healthcare Services Ltd | Wholesale & retail | 2023 |
| L Watfeh Capital Limited | Real estate | 2026 |
| L&V Traders Ltd | Wholesale & retail | 2025 |
| L.J.C. Contractors Ltd | Manufacturing | 2025 |
| LAB & Co Properties Ltd | Real estate | 2017 |
| Lacez Ltd | Wholesale & retail | 2026 |
| Lakezeolite Technologies Ltd | Construction | 2025 |
| Lala Kikobe Group Limited | Wholesale & retail | 2026 |
| Lamorna Estates Ltd | Real estate | 2022 |
| LANG2 Limited | Education | 2017 |
| Latitude Contract Interiors Limited | Administrative & support | 2012 |
| Latitude Interiors Limited | Wholesale & retail | 2005 |
| Latitude Wealth Strategies Limited | Financial services | 2024 |
| LDN Lifts Ltd | Construction | 2017 |
| LDS Bookkeeping & Payroll Services Ltd | Professional & scientific | 2002 |
| Leaf Garden Maintenance Ltd | Administrative & support | 2023 |
| Leeding Limited | Health & social care | 2017 |
| Lees Financial Services Limited | Financial services | 2025 |
| Lemdev Ltd | Information & communication | 2025 |
| LG Portfolio Limited | Real estate | 2010 |
| LGB Furnishings Limited | Construction | 2014 |
| Lilypads Day Nursery & Pre-School Ltd | Health & social care | 2012 |
| Limelight Media Productions Ltd | Information & communication | 2012 |
| Linda Charles Art & Design Ltd | Arts & recreation | 2023 |
| Lingobubble Limited | Education | 2020 |
| Link Medical Staffing Solutions Ltd | Health & social care | 2016 |
| Lippitt Fire Protection Ltd. | Construction | 2019 |
| Lishers Painting & Decorating Ltd | Construction | 2024 |
| Little Acorns Fostering Ltd | Health & social care | 2012 |
| Little Bradley Farm Company | Agriculture & fishing | 1976 |
| Little Gables Ltd | Real estate | 2017 |
| Little Raindrops | Education | 2010 |
| Little Thurlow Renewables Limited | Administrative & support | 2013 |
| Littlebond Ltd | Wholesale & retail | 2026 |
| Lizzie’S Homes Ltd | Real estate | 2023 |
| Ljdpp Limited | Real estate | 2017 |
| LMK Engineering Limited | Extraterritorial | 1984 |
| LMK Thermosafe Limited | Manufacturing | 2000 |
| Lobo Concepts Limited | Professional & scientific | 2008 |
| Logika Partitions Limited | Manufacturing | 1995 |
| Logika Systems Ltd | Manufacturing | 2011 |
| Logorunner Design Studio Limited | Professional & scientific | 2009 |
| Lokos Electronics UK Limited | Manufacturing | 2015 |