| Intersure Insurance Brokers Limited | Financial services | 2000 |
| Intersure Life and Pensions Limited | Extraterritorial | 2001 |
| Intraorbis Ltd | Administrative & support | 2004 |
| Inversion Aerobatics Ltd | Other services | 2025 |
| Ipswich Carpet & Flooring Limited | Construction | 2017 |
| Ipswich Floor Sanding Ltd | Construction | 2019 |
| Ipswich ST Edmund House RTM Company Ltd | Households | 2021 |
| Iris and the Moon Ltd | Wholesale & retail | 2024 |
| Ironbark Associates Ltd | Professional & scientific | 2019 |
| It's Happening Ltd | Information & communication | 2021 |
| It's Happening Studios Limited | Information & communication | 2023 |
| ITC Assets Limited | Hospitality | 2012 |
| ITM Construction Services Limited | Construction | 2017 |
| It’S Happening in Space Ltd | Information & communication | 2025 |
| IVY & Bond Ltd | Wholesale & retail | 2022 |
| J & D Fernando Limited | Wholesale & retail | 2025 |
| J & Sons Development Limited | Real estate | 2025 |
| J a Quinn Ltd | Other services | 2026 |
| J Bird Sales Limited | Wholesale & retail | 2025 |
| J G Corr Limited | Health & social care | 2011 |
| J Martin Consultancy Solutions Ltd | Professional & scientific | 2010 |
| J R Humphrey & SON Limited | Wholesale & retail | 2003 |
| J.A.B Carpentry Services Ltd | Manufacturing | 2022 |
| J.Jewell Limited | Wholesale & retail | 1969 |
| J.S.G Fencing and Gates Ltd | Construction | 2022 |
| J.T. Jewell Limited | Wholesale & retail | 1951 |
| Jabdec Ltd | Professional & scientific | 2025 |
| Jabe Holdings Limited | Financial services | 2019 |
| Jack Thorogood Limited | Financial services | 2026 |
| Jacob's Canvey Island Ltd | Wholesale & retail | 2013 |
| Jacoto Limited | Hospitality | 2013 |
| Jacs Venture Properties Ltd | Real estate | 2021 |
| Jaffna Retail Ltd | Wholesale & retail | 2020 |
| James a Allen Ltd | Information & communication | 2021 |
| James Duncan Limited | Real estate | 2011 |
| Jamie's Meat Inn Limited | Wholesale & retail | 2014 |
| Jan's Properties Ltd | Real estate | 2004 |
| Japanese Knotweed Protection Policy Ltd | Water & waste | 2016 |
| Java Caffe Limited | Extraterritorial | 2012 |
| Jayden Electrical Ltd | Energy | 2015 |
| JB Energy Services Ltd | Construction | 2023 |
| JB Plumbing & Heating (East Anglia) Ltd | Construction | 2022 |
| JC Building & Landscaping Ltd | Construction | 2025 |
| JCS Properties Limited | Extraterritorial | 1939 |
| JCT General Building Ltd | Construction | 2026 |
| JCW Exotics Ltd | Wholesale & retail | 2025 |
| JDB Trading Ltd | Wholesale & retail | 2026 |
| JDC Management Consulting Ltd | Professional & scientific | 2004 |
| JDS Accounting & Tax Services Ltd | Professional & scientific | 2017 |
| JEC Audio Limited | Wholesale & retail | 2014 |
| Jeff Edwards Consultancy Ltd | Professional & scientific | 2023 |
| Jenmain Builders Limited | Construction | 1972 |
| Jennifer Prowse Media Services Limited | Information & communication | 2000 |
| JET OFF Holidays Ltd | Administrative & support | 2023 |
| Jetforce Limited | Water & waste | 2021 |
| Jetha Aesthetics Ltd | Health & social care | 2020 |
| JFC Engineering Services Ltd | Professional & scientific | 2018 |
| Jignesh Patel Limited | Health & social care | 2012 |
| Jimbo Motors Ltd | Wholesale & retail | 2025 |
| Jjaie Limited | Real estate | 2022 |
| Jjay Property Lets Limited | Real estate | 2013 |
| JK Services Group Ltd | Transport & logistics | 2016 |
| JMD Decorators Limited | Construction | 2013 |
| JMO Transport Ltd | Transport & logistics | 2021 |
| Joadoor Limited | Real estate | 2025 |
| Jodieland Limited | Real estate | 2017 |
| John Bush Limited | Arts & recreation | 2011 |
| John Francis Costs Consultants Ltd | Professional & scientific | 2009 |
| Johnson's Independent Traders Limited | Wholesale & retail | 2020 |
| JON West Limited | Professional & scientific | 2009 |
| Jonathan Lambert Limited | Wholesale & retail | 2011 |
| Jonny Birkett Place Maker Ltd | Professional & scientific | 2025 |
| Joyson Safety Systems UK Ltd. | Manufacturing | 2014 |
| JPG Utilities Ltd | Construction | 2016 |
| JR & EH Nott Limited | Agriculture & fishing | 2016 |
| JRB Electrical (Suffolk) Ltd | Construction | 2025 |
| JRE Surveying Services Limited | Professional & scientific | 2025 |
| Jrhr Associates Limited | Administrative & support | 2012 |
| JS Howard Limited | Information & communication | 2025 |
| JSK Worldwide Enterprises Ltd | Information & communication | 2025 |
| JSL Medical Ltd | Education | 2026 |
| JT Carpentry Services Limited | Construction | 2008 |
| Jude’S Lunch Box Ltd | Hospitality | 2024 |
| Jukes Coulson Stokes & Company Limited | Other services | 1952 |
| Julian Cutter Limited | Other services | 2003 |
| Justin Stalls Limited | Other services | 2012 |
| Justpicked Produce Ltd | Wholesale & retail | 2020 |
| JW Violins Limited | Manufacturing | 2025 |
| K T Construction Limited | Construction | 1997 |
| K. Martin (Sudbury) Limited | Real estate | 1973 |
| Kaal Systems Limited | Information & communication | 2014 |
| Karl Lindekam (Sudbury) Limited | Other services | 2021 |
| KAY Coffee Company Ltd | Hospitality | 2020 |
| Kaymar Property Limited | Real estate | 2019 |
| KBM House Share & Property Management Ltd | Real estate | 2015 |
| KC Cool Van Ltd | Administrative & support | 2021 |
| Keep Falling Ltd | Information & communication | 2025 |
| Kelly Browne Training Ltd | Transport & logistics | 2025 |
| Kemlyn Consultants Ltd | Information & communication | 2010 |
| Kennet Heath Management (NO.2) Limited | Households | 2004 |