| A B Sea Logistics Ltd | Transport & logistics | 2018 |
| A C Construction (Colchester) Limited | Construction | 2008 |
| A C D Services (UK) Ltd | Water & waste | 2014 |
| A C Geotechnical and Environmental Services Ltd | Professional & scientific | 2020 |
| A C Landscape Contracts Limited | Administrative & support | 2010 |
| A C Motors (Colchester) Limited | Wholesale & retail | 2011 |
| A Clarke Carpets & Flooring Ltd | Construction | 2017 |
| A D Food Holdings Limited | Professional & scientific | 2006 |
| A D Mitchell Electrical Contractors Ltd | Manufacturing | 2013 |
| A D Mitchell Electrical Ltd | Construction | 2022 |
| A Day Long Limited | Information & communication | 2025 |
| A Dewar Ltd | Construction | 2010 |
| A Everitt Plumbing & Heating Limited | Construction | 2019 |
| A Four Estates Limited | Real estate | 2024 |
| A Four Exponents Limited | Information & communication | 2024 |
| A G Collectibles Ltd | Wholesale & retail | 2022 |
| A H Marine Consultants Ltd | Professional & scientific | 2025 |
| A J B Accountants Ltd. | Professional & scientific | 2004 |
| A J Bland Estates Ltd | Households | 2022 |
| A J Chaytor Flooring & Carpets Ltd | Wholesale & retail | 2019 |
| A J Contract Carpentry Ltd | Manufacturing | 2021 |
| A J Flooring Limited | Construction | 2005 |
| A J Leather Building Services Ltd | Construction | 2025 |
| A J Wildash Limited | Construction | 2005 |
| A Kerry Services Limited | Financial services | 2019 |
| A L Findings Ltd | Wholesale & retail | 2011 |
| A LA Mode Ltd | Other services | 2025 |
| A Larkins Engineering Ltd | Wholesale & retail | 2014 |
| A M Airport Shuttle Colchester Ltd | Transport & logistics | 2023 |
| A M Logistics & Warehousing Southern Ltd | Transport & logistics | 2013 |
| A M Roofing Specialists Ltd | Construction | 2020 |
| A Nagesh Limited | Professional & scientific | 2018 |
| A New Dawn Development Limited | Construction | 2025 |
| A P Contracts Ltd | Construction | 2006 |
| A Pearson Electrical Limited | Construction | 2009 |
| A Plus + Limited | Professional & scientific | 1999 |
| A R Mayers Limited | Wholesale & retail | 2003 |
| A Safe House Limited | Health & social care | 2019 |
| A Sharman Plumbing and Heating Ltd | Construction | 2023 |
| A Simple Goodbye Limited | Other services | 2019 |
| A Star Cleanz Limited | Administrative & support | 2016 |
| A Star Electrical Contractors Ltd | Construction | 2019 |
| A Willsher & SON Limited | Wholesale & retail | 2003 |
| A&A Commercial Services Ltd | Administrative & support | 2018 |
| A&D Plumbing Services Ltd | Construction | 2017 |
| A&D Transporting Ltd | Transport & logistics | 2015 |
| A&G Realty Ltd | Real estate | 2025 |
| A&L House of Beauty Ltd | Other services | 2022 |
| A&L Properties Management Limited | Real estate | 2025 |
| A&S Waterproof Liquids Ltd | Construction | 2020 |
| A'S Beauty Queens Ltd | Wholesale & retail | 2024 |
| A-Onee Limited | Wholesale & retail | 2019 |
| A-Team Paving Ltd | Construction | 2022 |
| A. Clarke Monumental Limited | Manufacturing | 2017 |
| A. Covey Property Maintenance Ltd | Construction | 2023 |
| A. Luvisiah and Company Ltd | Professional & scientific | 2014 |
| A. P. T. Farming Limited | Agriculture & fishing | 1947 |
| A. Watt. Electrical Ltd. | Construction | 2009 |
| A.B.D Care Services Ltd | Administrative & support | 2026 |
| A.C. Creative Photography Limited | Professional & scientific | 2002 |
| A.C.Flooring (Essex) Ltd | Construction | 2019 |
| A.D Assessments Limited | Health & social care | 2021 |
| A.D. James Ltd. | Construction | 2006 |
| A.D.S. Insurance Brokers Limited | Financial services | 1988 |
| A.F.I.P. Commercial Ltd | Manufacturing | 2017 |
| A.G. Tremain Limited | Construction | 1972 |
| A.G.R Electrics Ltd | Construction | 2025 |
| A.H Independent Consultant Limited | Health & social care | 2019 |
| A.J. Energy Consultants Limited | Professional & scientific | 2007 |
| A.J. Franklin & Sons Limited | Extraterritorial | 2002 |
| A.J.S. GAS & Heating Services Ltd | Manufacturing | 2002 |
| A.L. Contracts Contractors & Paving Specialists Ltd | Construction | 2019 |
| A.R Curtis (Groundworks) Limited | Construction | 2002 |
| A.R.K. Business Consultants Limited | Professional & scientific | 2019 |
| A.Riley Electrical Ltd | Construction | 2021 |
| A.S. Meakin Ltd | Wholesale & retail | 2019 |
| A.S.A.P Accounting Services Ltd | Professional & scientific | 2004 |
| A.S.C Medical Services Ltd | Health & social care | 2021 |
| A.T.E. Fire Protection Limited | Construction | 1993 |
| A.T.E. Property Developments Limited | Real estate | 2020 |
| A.W. Lifting Limited | Construction | 2011 |
| A/A Modern Kitchen Ltd | Hospitality | 2026 |
| A1 Best Traders Ltd | Transport & logistics | 2018 |
| A1 Quality Home Care Limited | Health & social care | 2004 |
| A25 Solutions Ltd | Health & social care | 2019 |
| A2B Courier Services Limited | Transport & logistics | 2020 |
| A2B Electrics Ltd | Construction | 2024 |
| A2B Ltd | Professional & scientific | 2015 |
| A2Z Safety Ltd | Construction | 2020 |
| A3D Solutions Limited | Professional & scientific | 2025 |
| A5CEND Limited | Professional & scientific | 2018 |
| AA Omer Traders Ltd | Wholesale & retail | 2025 |
| AA Power Consulting Ltd | Administrative & support | 2016 |
| AA Seller Hub Ltd | Wholesale & retail | 2025 |
| AA Trading & Investments Ltd | Financial services | 2021 |
| AA Trans Limited | Transport & logistics | 2019 |
| AAA Plus Properties Ltd | Real estate | 2025 |
| Aaac Limited | Energy | 2005 |
| AAB Cheap Skips Ltd | Water & waste | 2025 |
| Aabco Hydraulics Limited | Other services | 2003 |