| Integra Wellbeing & Performance Ltd | Health & social care | 2025 |
| Integrity PAT Testing Ltd | Other services | 2021 |
| International Port Community Systems Association Ukeig | | 2011 |
| Ionut Logistic Solutions Ltd | Transport & logistics | 2020 |
| Iordan Trans Ltd | Transport & logistics | 2026 |
| Iosif Trans Ltd | Transport & logistics | 2019 |
| Ipax Palace Limited | Hospitality | 2026 |
| Ipswich Electrical Ltd | Construction | 2020 |
| Ipswich Law Limited | Professional & scientific | 2014 |
| Ipswich Phoenix Basketball Club C.I.C. | Arts & recreation | 2025 |
| Ipswich Van Hire Ltd | Administrative & support | 2018 |
| Iron Monk Studios Ltd | Information & communication | 2021 |
| Itachem UK Limited | Transport & logistics | 2014 |
| Ivko Ltd | Transport & logistics | 2013 |
| J M Symonds Ltd | Wholesale & retail | 2015 |
| J&S Recovery Limited | Transport & logistics | 2019 |
| J.K.D.C. Limited | Information & communication | 2016 |
| J.L. Knight Roadworks Limited | Construction | 1977 |
| J.Nightingale Ltd | Manufacturing | 2019 |
| Jade Yourell Limited | Financial services | 2021 |
| Jaki Trans Ltd | Transport & logistics | 2026 |
| James Hunt Fisheries Limited | Administrative & support | 2018 |
| James Kemball Limited | Transport & logistics | 1973 |
| Janor Trans Ltd | Transport & logistics | 2021 |
| Jason 1 Ltd | Transport & logistics | 2018 |
| JB Accounting & Bookkeeping Ltd | Professional & scientific | 2025 |
| JB Property Management Limited | Real estate | 2015 |
| JBH Homes Limited | Real estate | 2019 |
| JC Ryder Limited | Wholesale & retail | 2016 |
| JD Cargo Transport Ltd | Transport & logistics | 2021 |
| JD Container Transport Ltd | Transport & logistics | 2020 |
| Jeff Coleman Wealth Management Limited | Financial services | 2011 |
| JFH Transport Ltd | Transport & logistics | 2020 |
| Jiezhong (UK) INT Co. Ltd | Transport & logistics | 2021 |
| Jigsaw Mortgages Felixstowe Ltd | Financial services | 2019 |
| JKO Procurement Services Limited | Transport & logistics | 2018 |
| JLP and SON Transport Ltd | Transport & logistics | 2024 |
| JOE Hearne Enterprises Ltd | Financial services | 2017 |
| John Hatcher & Company Limited | Agriculture & fishing | 1977 |
| John Scrutton Investments Limited | Real estate | 1998 |
| JON Transport Limited | Transport & logistics | 2018 |
| Jordon Freight Limited | Transport & logistics | 1999 |
| Jordon Holdings Limited | Financial services | 2016 |
| Jovilag Ltd | Transport & logistics | 2022 |
| JP 1191 Limited | Hospitality | 2026 |
| JRD Property Improvements Ltd | Construction | 2025 |
| Jupiter Collects Ltd | Wholesale & retail | 2026 |
| Jurij Volkov Limited | Transport & logistics | 2020 |
| Juszt Watches Ltd | Wholesale & retail | 2026 |
| K W L Logistics Limited | Transport & logistics | 1996 |
| K&A Transport Ltd | Transport & logistics | 2007 |
| K&S (979) Limited | Transport & logistics | 2012 |
| Kaleidoscope Results Coaching Ltd | Health & social care | 2006 |
| Kapak Limited | Transport & logistics | 2020 |
| Karbon Electrical Ltd | Construction | 2026 |
| Kate's Maid Service Ltd | Administrative & support | 2016 |
| Katy Ellen Snelgrove Ltd | Professional & scientific | 2024 |
| KAY Hallinan Properties Limited | Real estate | 2025 |
| Kayu Limited | Real estate | 2000 |
| Kcbb Services Ltd. | Professional & scientific | 2014 |
| KDR European Limited | Transport & logistics | 2011 |
| Kedan Logistics Limited | Transport & logistics | 2005 |
| Kerry Addison Limited | Financial services | 2016 |
| Kevin Lawrenson Transport Limited | Transport & logistics | 2015 |
| Key Psychology Ltd | Education | 2024 |
| Keyshare Living Ltd | Real estate | 2025 |
| Kids Therapy Works Limited | Health & social care | 2010 |
| Kiligarth Court (Felixstowe) Limited | Construction | 2006 |
| Kiligarth Court Management Services Ltd | Households | 2008 |
| Kimberley and Matthew Goodwin Limited | Wholesale & retail | 2025 |
| Kingsfleet Ltd | Professional & scientific | 2022 |
| Kingsfleet Property Limited | Construction | 2024 |
| Kirton and Trimley Community Action Group Ltd | Other services | 2018 |
| Kirton Kites Ltd | Education | 2024 |
| KIS Quilting Events Ltd | Arts & recreation | 2026 |
| KIS Quilting Limited | Wholesale & retail | 2014 |
| Kitchens Continental (Suffolk) Limited | Construction | 2007 |
| Kitz Home Limited | Other services | 2024 |
| KJO Creative Ltd | Information & communication | 2026 |
| KLA Transport Ltd | Transport & logistics | 2019 |
| Klank Limited | Professional & scientific | 2014 |
| KLM Haulage Ltd | Transport & logistics | 2015 |
| Kmart Consulting Ltd | Information & communication | 2014 |
| KMU Kitchen Ltd | Hospitality | 2025 |
| Knight Roadworks (2010) Limited | Professional & scientific | 2010 |
| Kocabey Ltd | Wholesale & retail | 2020 |
| Kohinoor Foods (UK) Limited | Extraterritorial | 2004 |
| Kohinoor Foods Limited | Extraterritorial | 2008 |
| Kolaitis Ltd | Transport & logistics | 2022 |
| Kpopuk Limited | Information & communication | 2017 |
| Kristina 17 Ltd | Transport & logistics | 2025 |
| KSI Portlink Limited | Transport & logistics | 2008 |
| Kubot Property Ltd | Wholesale & retail | 2017 |
| L D Richardson Builder & Contractor Limited | Construction | 2008 |
| L V Shipping Limited | Transport & logistics | 1983 |
| L&A Walter Ltd | Transport & logistics | 2024 |
| LA Casa Latina Ltd | Hospitality | 2023 |
| LA Vida Entertainment Ltd | Hospitality | 2022 |
| Laceys Fitness Ltd | Professional & scientific | 2007 |
| Laker Innovation Ltd | Professional & scientific | 2020 |