| + Added Music Limited | Information & communication | 2006 |
| 00001 Limited | Professional & scientific | 2025 |
| 00002 Limited | Professional & scientific | 2025 |
| 00733662 Limited | | 1962 |
| 111 Springfield Road Limited | Real estate | 1989 |
| 12/10 Constructions Ltd | Construction | 2026 |
| 122 Queens Road Bury ST. Edmunds Management Company Limited | Households | 1973 |
| 158 Productions Ltd | Information & communication | 2014 |
| 1ST Atlas Ltd | Wholesale & retail | 2022 |
| 247 Shopfronts and Repairs Ltd | Construction | 2023 |
| 24MSA Holdings Ltd | Financial services | 2024 |
| 28CORP Ltd | Wholesale & retail | 2024 |
| 29 Cavendish Road (Felixstowe) Freehold Limited | Households | 2025 |
| 44 Orwell Road Management Company Limited | Hospitality | 1997 |
| 44.1 Creative Limited | Information & communication | 1999 |
| A & a Transport Services | | 1988 |
| A B Falco & SON Ltd | Construction | 2003 |
| A B Homes Suffolk Limited | Real estate | 2005 |
| A Boake Roberts and Company (Holding) Limited | Professional & scientific | 1897 |
| A Mothers Power CIC | Education | 2025 |
| A. Calver (Electrical) Ltd | Construction | 2003 |
| A.Cutts Plumbing & Heating Limited | Construction | 2002 |
| A.D. Design Consultants Limited | Administrative & support | 2001 |
| A.H. Slater & Co. Limited | Agriculture & fishing | 1974 |
| A.W. & D. Hammond Limited | Wholesale & retail | 1970 |
| A2B-ONLINE Limited | Transport & logistics | 2006 |
| A3-A4 Limited | Wholesale & retail | 2024 |
| Abacus Colchester Limited | Financial services | 2007 |
| Abbey Glass Limited | Construction | 1992 |
| Abbey Security Services Ltd | Administrative & support | 1997 |
| Abbeygate Ceramic Tiles Limited | Wholesale & retail | 2005 |
| Abbeygate Lighting Limited | Wholesale & retail | 1997 |
| ABC Childcare (Ipswich) Ltd | Education | 2005 |
| Abco Insurance Services Limited | Financial services | 2003 |
| Absolute Angels Limited | Education | 2003 |
| Absolute Refrigeration Limited | Manufacturing | 2002 |
| Acc-Sys Software Limited | Information & communication | 1991 |
| Accountingwizards Limited | Information & communication | 1997 |
| Accurate Payroll Management Ltd | Professional & scientific | 2024 |
| ACENET3 LLP | | 2025 |
| Acorn Farms Limited | Agriculture & fishing | 1985 |
| Acorn Studio Press Ltd | Information & communication | 2025 |
| Acquired Properties Ltd | Real estate | 2023 |
| Action Outdoors Holidays Limited | Administrative & support | 2004 |
| Adecar Property Limited | Real estate | 2016 |
| Adehealthlinks Limited | Health & social care | 2015 |
| Adents Property Ltd | Real estate | 2023 |
| Adnams PLC | Manufacturing | 1890 |
| Aerlo Limited | Other services | 2025 |
| Aethris Ltd | Information & communication | 2020 |
| AFA Associates Ltd | Professional & scientific | 2023 |
| Affilion Ltd | Information & communication | 2024 |
| Afflutech Limited | Information & communication | 2024 |
| Afiashea Ltd | Wholesale & retail | 2021 |
| Afrobites Mixes UK Ltd | Hospitality | 2025 |
| Afrotility Limited | Education | 2024 |
| AG Solar Energy Ltd | Construction | 2026 |
| Agcm Ltd | Construction | 2019 |
| Ahlb Ltd | Professional & scientific | 2026 |
| AHO Consulting Ltd | Information & communication | 2021 |
| Ahoh Ltd | Health & social care | 2026 |
| Aifutur Education Ltd | Education | 2026 |
| Ainger (Holbrows) Limited | Wholesale & retail | 1991 |
| Airblast (East Anglia) Limited | Administrative & support | 1999 |
| Akfg Ltd | Financial services | 2025 |
| Akira Corp Ltd | Wholesale & retail | 2023 |
| Akira Gear Ltd | Wholesale & retail | 2023 |
| Akira Group Ltd | Wholesale & retail | 2023 |
| Alafia Care Provider Ltd | Health & social care | 2023 |
| Alan Howarth Limited | Construction | 1988 |
| Alan Ward Blinds Limited | Construction | 2008 |
| Alankrita's Enterprise Ltd | Health & social care | 2023 |
| Alansons Tooling Limited | | 1967 |
| Alberalkirk Ltd | Wholesale & retail | 2024 |
| Albert E. Webb & Sons (Long Melford) Limited | Wholesale & retail | 1977 |
| Albert Edward Stevens Ltd | Wholesale & retail | 2024 |
| Albert Jarvis Limited | Real estate | 1995 |
| Alchemy Wines Limited | Hospitality | 2001 |
| Aldeburgh Bookshop Limited | Wholesale & retail | 1970 |
| Aldeburgh Fish & Chip Shop Company Limited | Hospitality | 2003 |
| Aldeburgh Yacht Club | Other services | 2005 |
| Alder Tree Limited | Manufacturing | 2007 |
| Alel Sheq Solutions Ltd | Professional & scientific | 2023 |
| Alfa-European Limited | Extraterritorial | 2000 |
| Alhuwayni Ltd | Wholesale & retail | 2026 |
| Alimentation Limited | Arts & recreation | 2002 |
| ALL in One Shop Apacino Ltd | Wholesale & retail | 2025 |
| Allard Investment Corporation Limited | Extraterritorial | 2001 |
| Allendale Logistics Ltd | Transport & logistics | 2000 |
| Alltech (London) Limited | Information & communication | 1982 |
| Alnic Enterprises Ltd. | Professional & scientific | 1998 |
| Alperton Investments Limited | Extraterritorial | 2006 |
| Alpha Omega Property Maintenance and Construction Ltd | Construction | 2020 |
| Alphatech Designs Limited | Extraterritorial | 2000 |
| Altea Solutions Ltd | Professional & scientific | 2013 |
| Altek Ltd | Wholesale & retail | 2003 |
| Altkuz Circular Economy Ltd | Water & waste | 2024 |
| Amada Weld Tech Limited | Manufacturing | 1983 |
| Ambit Assets Ltd | Financial services | 2006 |
| Ambit Maintenance Ltd | Manufacturing | 2006 |