| Anderson Incorporation Ltd | Financial services | 2023 |
| Anderson Rose Limited | Real estate | 2011 |
| Andlee Insulation Services Ltd | Construction | 2019 |
| Andrews Timber & Plywood Limited | Real estate | 1978 |
| Andy Brunton Executive Search Limited | Other services | 2021 |
| Andy Wood Coaching Ltd | Education | 2025 |
| Angela's Boutique Ltd | Wholesale & retail | 2013 |
| Anglia Feeds Limited | Extraterritorial | 2023 |
| Anglia Press Agency Limited | Information & communication | 1971 |
| Anglia Restoration Ltd | Manufacturing | 2018 |
| Anirvaan Limited | Information & communication | 2018 |
| Antagonistsuk Ltd | Wholesale & retail | 2024 |
| Antestare Limited | Professional & scientific | 2017 |
| Anthsi Interactive Ltd | Wholesale & retail | 2020 |
| Antique Ring Boutique Ltd | Wholesale & retail | 2017 |
| Antworkz Limited | Real estate | 2018 |
| Anyg Ltd | Professional & scientific | 2025 |
| APA 4 Limited | Hospitality | 2019 |
| Apex Mouthguards Essex Ltd | Health & social care | 2025 |
| APEX27 Limited | Professional & scientific | 2020 |
| Apollo Audio Hertford Limited | Education | 2020 |
| Apollo Works Limited | Information & communication | 2000 |
| Apperly Developments Ltd | Households | 2025 |
| Apple 2000 Limited | Wholesale & retail | 1995 |
| Applpay Limited | Professional & scientific | 2025 |
| Appointmoor (Property Management Services) Ltd | Real estate | 1998 |
| Appointmoor Estates Limited | Real estate | 1998 |
| Appointmoor Limited | Real estate | 1993 |
| AR & Sons Joinery Solutions Ltd | Construction | 2017 |
| Arcady Architects Limited | Professional & scientific | 2004 |
| Arch Plumbing & Heating Limited | Construction | 2025 |
| Architectural Acoustic Solutions Ltd | Construction | 2020 |
| Archway Renovations Ltd | Real estate | 2025 |
| Arcus Projects Limited | Construction | 2025 |
| Argosy Toys Ltd | Wholesale & retail | 2020 |
| Armdale Consultation Ltd | Professional & scientific | 2023 |
| Armourflex Sports Limited | Manufacturing | 2013 |
| Artemis Gym Ltd | Arts & recreation | 2017 |
| Arwin Developments (Wellow) Limited | Construction | 2025 |
| ASE Design & Development Limited | Professional & scientific | 2001 |
| ASH Assets Limited | Transport & logistics | 2015 |
| Ashingdon Heights Limited | Real estate | 2006 |
| Ashingdon Maintenance Company Limited | Households | 1988 |
| Ashingdon Steel Solutions Ltd | Manufacturing | 2025 |
| Ashleigh Consulting Services Limited | Information & communication | 2007 |
| Ashleigh Houses Limited | Professional & scientific | 2014 |
| ASM Solutions Ltd | Information & communication | 2006 |
| ASN Professional Services Limited | Information & communication | 2015 |
| Assurco Limited | Administrative & support | 2021 |
| Assynt Holdings Limited | Administrative & support | 2019 |
| Aston Haulage Limited | Transport & logistics | 2016 |
| Astra Court (Maintenance) Limited | Households | 1977 |
| Astra Ventures Ltd | Financial services | 2023 |
| Astute IT Limited | Information & communication | 2014 |
| Atai Compliance Ltd | Professional & scientific | 2023 |
| ATC Certification Limited | Administrative & support | 2021 |
| ATC Utilities Limited | Construction | 2023 |
| Athena Environmental Solutions Limited | Professional & scientific | 2010 |
| Atkins Property Investments Limited | Real estate | 2024 |
| Atlantic Audio Studios Ltd | Information & communication | 2019 |
| Audley Court RTM Company Limited | Households | 2020 |
| Austin Barber Design Limited | Administrative & support | 2007 |
| Automotive Vehicle Services Ltd | Wholesale & retail | 2026 |
| Aventus Facilities Management Limited | Construction | 2020 |
| Avenue 9 Admin Services Ltd | Administrative & support | 2023 |
| Aviation Marketing Consultants Industries Limited | Manufacturing | 1982 |
| Avid Computers Ltd | Information & communication | 2009 |
| Avocet Care & Support Ltd | Hospitality | 1969 |
| Avondale Care Home Limited | Health & social care | 2015 |
| AW Glazing Installations Ltd | Construction | 2021 |
| AW Transport & Services Ltd | Wholesale & retail | 2022 |
| AW Vehicle Security Limited | Wholesale & retail | 2025 |
| Awesome & Awesome Ltd | Real estate | 2023 |
| Ayanza Joinery Limited | Construction | 2025 |
| Ayeye IO Limited | Information & communication | 2004 |
| Azreal Ltd | Financial services | 2024 |
| Aztec Media Services Ltd | Administrative & support | 2023 |
| Aztec Rentals Limited | Real estate | 2025 |
| B & V Holdings Limited | Professional & scientific | 2015 |
| B a Stewart Limited | Education | 2020 |
| B Eden Homes Ltd | Construction | 2022 |
| B W J Services Ltd | Construction | 2006 |
| B-Bling* Ltd | Wholesale & retail | 2020 |
| B-Secured Limited | Administrative & support | 2012 |
| Baby Sensory (South Essex) Limited | Education | 2010 |
| Baker Street Ltd | Wholesale & retail | 2015 |
| Balgores Properties Limited | Construction | 2011 |
| Ballers Brands Ltd | Wholesale & retail | 2019 |
| Baltic Distribution Limited | Extraterritorial | 2026 |
| Baltic Wharf Properties Limited | Real estate | 2015 |
| Barber and Smith Tiling Limited | Construction | 2019 |
| Barber Rentals Limited | Real estate | 2017 |
| Barbican Building Services Ltd | Construction | 2019 |
| Barford Contractors Limited | Administrative & support | 2004 |
| Barker Electrical Solutions Limited | Construction | 2019 |
| Barnes Lewis Consultants Limited | Information & communication | 1996 |
| Barton Trade Credit Risk Services Limited | Construction | 2011 |
| Bathroom Consultants Limited | Professional & scientific | 2022 |
| BBB Productions Limited | Information & communication | 2015 |
| Beach Peach Ltd | Wholesale & retail | 2021 |