| J.R.B. Assessors Ltd | Professional & scientific | 2011 |
| J.Smith & SON Driveways Ltd | Construction | 2026 |
| J.Smith & SON Ltd | Construction | 2023 |
| J.Smith & SON Roofing & Building Ltd | Construction | 2024 |
| J2E2 Limited | Professional & scientific | 2016 |
| J90 Holdings Ltd | Administrative & support | 2018 |
| J90 Property Ltd | Real estate | 2019 |
| Jack Charles Brickwork Ltd | Construction | 2018 |
| Jack Khurana Limited | Professional & scientific | 2015 |
| Jack Nancy Construction Solutions Ltd | Construction | 2026 |
| Jacks for Women Ltd | Wholesale & retail | 2019 |
| JAM Home Investments Ltd | Real estate | 2023 |
| James Craig Consultancy Ltd | Professional & scientific | 2025 |
| James Lewy Finance Limited | Financial services | 2010 |
| James Property Ltd | Construction | 2024 |
| Jammydog Investments Ltd | Information & communication | 2017 |
| Janay Ltd | Wholesale & retail | 2014 |
| Jane Baross-Evans Freelance Designer Ltd | Professional & scientific | 2018 |
| Jane Humphries Ltd | Other services | 2021 |
| Janet Nelson Limited | Arts & recreation | 2016 |
| Jarvis James Consulting Ltd | Administrative & support | 2024 |
| Jasmine Ward Ltd | Arts & recreation | 2013 |
| Jay's Cars Limited | Wholesale & retail | 2002 |
| Jbgraphs Ltd | Professional & scientific | 2023 |
| JBR Consult Ltd | Information & communication | 2024 |
| Jdgray Associates Limited | Construction | 2011 |
| JDK Building Services Ltd | Construction | 2024 |
| Jeanart Foods Limited | Hospitality | 2013 |
| Jeanneret Ltd | Manufacturing | 2007 |
| Jefferson Payroll & Accountancy Ltd | Professional & scientific | 2015 |
| Jefferson Payroll Bureau Ltd | Professional & scientific | 2010 |
| Jemport Limited | Manufacturing | 1994 |
| Jenifer Richmond Executive Coaching Limited | Professional & scientific | 2014 |
| Jenko Dynamics Limited | Information & communication | 2025 |
| Jennings Estates Limited | Real estate | 2001 |
| Jerman Consultants Ltd | Information & communication | 2011 |
| Jetoff Limited | Wholesale & retail | 2024 |
| JF Mckenzie Limited | Professional & scientific | 2023 |
| JG Architecture LLP | | 2025 |
| JH Consulting Services Ltd | Information & communication | 2024 |
| JHB Healthcare Limited | Real estate | 2014 |
| JHJ Frisby Limited | Hospitality | 2022 |
| Jigballs Media Ltd | Information & communication | 2025 |
| JIM Club Ltd | Arts & recreation | 2020 |
| JJC Trading Ltd | Administrative & support | 2016 |
| Jkml Consulting Ltd | Professional & scientific | 2024 |
| JLF Food Services Ltd | Hospitality | 2019 |
| Jlockwoodconsultant Ltd | Professional & scientific | 2026 |
| JM Ashworth Ltd | Transport & logistics | 2021 |
| JMC Building Surveying Limited | Professional & scientific | 2015 |
| JMC Design and Motion Limited | Administrative & support | 2014 |
| JMS Domus Limited | Real estate | 2024 |
| Jmwr Ltd | Real estate | 2021 |
| JNW Associates Ltd | Professional & scientific | 2011 |
| Joag Ltd | Information & communication | 2021 |
| JOE Rice Property Ltd | Real estate | 2022 |
| JOE Sadler Limited | Professional & scientific | 2009 |
| John Dillon Limited | Other services | 2003 |
| Johnson Robert Land Limited | Administrative & support | 2011 |
| Johnson Tilley Associates Limited | Professional & scientific | 2003 |
| Jojo Properties Limited | Households | 2019 |
| JON Elliott Designs Limited | Other services | 2020 |
| Jonathan Barratt Consulting Ltd | Health & social care | 2017 |
| Jonathan Farrell Limited | Financial services | 2016 |
| Jones Cleaning Services Limited | Administrative & support | 2012 |
| Jords & Co Ltd | Information & communication | 2023 |
| Joshua Thomas Media Limited | Manufacturing | 2016 |
| Jostaberry Ltd | Hospitality | 2018 |
| Journey Sure Ltd | Financial services | 2019 |
| JP Building Developments Limited | Construction | 2019 |
| JPS Trading Services Ltd | Wholesale & retail | 2019 |
| JRB Plumbing and Heating Services Ltd | Construction | 2015 |
| JS Book-Keeping & Accountancy Ltd | Professional & scientific | 2002 |
| JS Scaffolding Services Ltd | Construction | 2020 |
| JSJ Security Limited | Administrative & support | 2021 |
| JSP24 Limited | Real estate | 2021 |
| JT Refurbishments Ltd | Wholesale & retail | 2026 |
| Jump Joinery Limited | Construction | 2019 |
| Jump Lets Ltd | Real estate | 2021 |
| Jumpd Customer Engineering Limited | Professional & scientific | 2014 |
| Jungle Berry Partners Ltd | Wholesale & retail | 2025 |
| Just INK & Toners Ltd | Wholesale & retail | 2020 |
| Justin Lack Limited | Construction | 2003 |
| Justin Time Properties Limited | Households | 2024 |
| Jute Coffee Limited | Manufacturing | 2018 |
| JW Carpentry & Joinery Limited | Construction | 2019 |
| JW Global Services Limited | Wholesale & retail | 2024 |
| JW Quality Consulting Ltd | Professional & scientific | 2011 |
| JW Signs & Graphics Limited | Professional & scientific | 2018 |
| JWA Architecture Limited | Professional & scientific | 1995 |
| K Lewington Heating & GAS Specialists Limited | Manufacturing | 2004 |
| K Topham Roofing Ltd | Construction | 2016 |
| K. Langrick Consulting Limited | Professional & scientific | 2015 |
| K.C.S Cleaning Services Ltd | Administrative & support | 2017 |
| K.R. Building & Carpentry Limited | Construction | 2023 |
| Kairos Medical Ltd | Health & social care | 2023 |
| Kajo Property Solutions Ltd | Real estate | 2023 |
| Kalen Tattersall Ltd | Wholesale & retail | 2024 |
| Kanyi Assist Ltd | Transport & logistics | 2025 |
| Kate Please Ltd | Wholesale & retail | 2020 |