| Aadi's Kitchen Ltd | Wholesale & retail | 2022 |
| Aaditya Travel Limited | Transport & logistics | 2023 |
| Aadvs Software Limited | Information & communication | 2025 |
| Aardvark Equipment Ltd | Manufacturing | 1999 |
| Aardwolf Solutions Ltd | Information & communication | 2014 |
| Aarem Commercial Ltd | Real estate | 2021 |
| Aarem Holdings Ltd | Financial services | 2018 |
| Aarem Limited | Administrative & support | 2017 |
| Aarem Properties Ltd | Real estate | 2018 |
| Aaria Retail UK Ltd | Wholesale & retail | 2021 |
| Aaron James Security Consultancy Limited | Administrative & support | 2024 |
| Aaron Landscapes Limited | Administrative & support | 2010 |
| Aart DK Ltd | Transport & logistics | 2019 |
| Aarvi Properties Ltd | Real estate | 2024 |
| AAV Construction Limited | Construction | 2011 |
| Aayan Consulting Ltd | Information & communication | 2022 |
| AB & HB Property Limited | Real estate | 2022 |
| AB Beauty Salon Colchester Ltd | Other services | 2024 |
| AB Electrical Contractors Limited | Construction | 2009 |
| AB Keepers Ltd | Extraterritorial | 2020 |
| ABA Somno Ltd | Health & social care | 2018 |
| Abacus Build (UK) Ltd | Construction | 2008 |
| Abacus Build Ltd | Construction | 2004 |
| Abacus Group Holdings Ltd | Financial services | 2019 |
| Abacus Learning LLP | | 2012 |
| Abacus Little Learners LLP | | 2023 |
| Abacus Master Locksmiths Limited | Extraterritorial | 2004 |
| Abacus Project Services Limited | Professional & scientific | 1992 |
| Abacus Shutters Ltd | Manufacturing | 1999 |
| Abak Systems and Investment Limited | Information & communication | 2007 |
| Abba Consulting Ltd | Information & communication | 2022 |
| Abberton Business Park Ltd | Real estate | 2014 |
| Abberton Car Sales Ltd | Wholesale & retail | 2024 |
| Abbey Gardens (Thorpe-Le-Soken) Management Company Limited | Households | 2018 |
| Abbey House (Colchester) Limited | Households | 2014 |
| Abbey Motors Colchester Ltd | Wholesale & retail | 2011 |
| Abbey Property Services(Essex) Ltd | Other services | 2011 |
| Abbeygate Two RTM Company Limited | Households | 2020 |
| Abbo Investments Limited | Construction | 2016 |
| Abbots Colchester Management 2016 Limited | Real estate | 2016 |
| Abbots Road (Colchester) Management Company Limited | Households | 1990 |
| Abbotts Carpentry Limited | Construction | 2010 |
| Abbylat Healthcare Services Ltd | Health & social care | 2016 |
| ABC Accountancy Services (UK) Ltd | Professional & scientific | 2017 |
| Abcrecruitment.Jm Ltd | Administrative & support | 2026 |
| Abdollahi FBA Ltd | Wholesale & retail | 2023 |
| Abdollahi Properties Limited | Real estate | 2022 |
| Abdullah's Lily Limited | Construction | 2010 |
| Aber Electronics Limited | Manufacturing | 2010 |
| Abermek Limited | Real estate | 1984 |
| Abhiksha Ltd | Administrative & support | 2018 |
| ABI Valves Ltd | Professional & scientific | 2021 |
| Abigail's Collection Ltd | Wholesale & retail | 2012 |
| Ability Physiotherapy Ltd | Health & social care | 2019 |
| Ability Using Sport C.I.C. | Education | 2019 |
| ABJ Straw Tendring Limited | Agriculture & fishing | 2024 |
| Able Marquees 1 Ltd | Hospitality | 2019 |
| Able Renewables Ltd | Construction | 2019 |
| Abletech Electronics Limited | Manufacturing | 2003 |
| Ablewhite Surveyors Limited | Real estate | 2023 |
| ABM Sales Limited | Professional & scientific | 2010 |
| Abmark Ltd | Households | 2011 |
| Abode Projects Essex Ltd | Construction | 2020 |
| Abounding Properties Ltd | Other services | 2024 |
| Above & Beyond Cleaning Services Ltd | Administrative & support | 2021 |
| Above Board Storage Solutions Ltd | Manufacturing | 2026 |
| Above Plumbing and Heating Limited | Construction | 2016 |
| Above Surveying Ltd | Information & communication | 2013 |
| Abpc Medicsolutions Ltd | Administrative & support | 2016 |
| Abpcsolutions Ltd | Information & communication | 2012 |
| Abrehart Property Ltd | Real estate | 2020 |
| Abroa Capital Limited | Professional & scientific | 2021 |
| Abroa Property Group Limited | Financial services | 2021 |
| Absolute Building Contractors (Colchester) Limited | Construction | 2023 |
| Absolute Building Contractors Limited | Construction | 1995 |
| Absolute Candour Ltd | Professional & scientific | 2026 |
| Absolute Party Cruises (London) Limited | Hospitality | 2010 |
| Absolute Value Limited | Education | 2019 |
| AC & GS Properties Limited | Real estate | 2008 |
| AC Applications Limited | Professional & scientific | 2023 |
| AC BC Ltd | Administrative & support | 2023 |
| AC Greatti Limited | Professional & scientific | 2024 |
| AC ION Ltd | Transport & logistics | 2020 |
| AC Pro Ltd | Manufacturing | 2025 |
| ACA Asset Holdings Ltd | Financial services | 2025 |
| ACA Couriers Ltd | Transport & logistics | 2025 |
| Acacia Park Residents Management Company Limited | Households | 2012 |
| Acca Consultancy Private Limited | Health & social care | 2014 |
| Accelerator Pro Limited | Administrative & support | 2022 |
| Access Creative Services Ltd | Information & communication | 2019 |
| Accessible Access Solutions Ltd | Professional & scientific | 2012 |
| Accj Properties Limited | Real estate | 2002 |
| Accolade Software Limited | Information & communication | 1984 |
| Accountable Care Enterprise Limited | Health & social care | 2017 |
| ACCOUNTANT360.CO.UK Ltd | Professional & scientific | 2019 |
| Accountants Direct (Essex) Ltd | Professional & scientific | 2017 |
| Accredited Heating (Commercial) Ltd | Construction | 2020 |
| Accredited Heating Services Ltd | Households | 2008 |
| Accumark Management & Accountancy Ltd | Professional & scientific | 2025 |
| Ace 24 Group Ltd | Real estate | 2013 |