| Aston Martin Heritage Limited | Professional & scientific | 1990 |
| Aston Shaw Financial Planning Ltd | Extraterritorial | 2020 |
| Aston Shaw Limited | Professional & scientific | 2005 |
| Aston Shaw Restructuring Ltd | Extraterritorial | 2015 |
| Astonmaster Consulting Ltd | Professional & scientific | 2010 |
| Astoria Property Services Limited | Construction | 2016 |
| Astoundme Ltd | Information & communication | 2015 |
| Astra Frame Limited | Manufacturing | 1995 |
| Astra NO.1 (NMR) Ltd | Real estate | 2025 |
| Astra NO.2 (WLW) Ltd | Real estate | 2025 |
| Astra NO.3 (FOX) Ltd | Real estate | 2026 |
| Astra NO.4 (BLR) Ltd | Real estate | 2026 |
| Astra NO.5 (RCR) Ltd | Real estate | 2026 |
| Astra NO.6 (WAL) Ltd | Real estate | 2026 |
| Astra NO.7 (TUD) Ltd | Real estate | 2026 |
| Astrada Ltd | Wholesale & retail | 2025 |
| Astral Aviation Consulting Ltd | Professional & scientific | 2020 |
| Astralabe Vista Ltd | Construction | 2025 |
| Astrid Paige and Grace Ltd | Real estate | 2021 |
| Astris Homes East Anglia Limited | Construction | 2015 |
| Astwood Energy Centre Limited | Energy | 2023 |
| ASV Lowestoft Limited | Hospitality | 2019 |
| ASW Homes Ltd | Real estate | 2022 |
| ASW Property Investors Limited | Real estate | 2022 |
| ASW Real Estate Ltd | Real estate | 2024 |
| Asyries Buzi Concept Limited | Health & social care | 2023 |
| AT EAT Stalham Ltd | Hospitality | 2024 |
| AT Home Properties Norfolk Limited | Real estate | 2021 |
| AT Your Convenience Builders Ltd. | Construction | 2023 |
| Atab Property Ltd | Hospitality | 2025 |
| Atac NR Limited | Hospitality | 2024 |
| Atalanta Advisory Limited | Administrative & support | 2018 |
| Ataraxia Property Limited | Real estate | 2025 |
| ATB Group UK Limited | Manufacturing | 2007 |
| ATB Laurence Scott Limited | Manufacturing | 2015 |
| ATB Morley Limited | Manufacturing | 2000 |
| Atbloomfieldproperties Ltd | Real estate | 2019 |
| Atek Beverley Limited | Wholesale & retail | 2017 |
| Atelier (NFK) Ltd | Other services | 2016 |
| Atelier at Property LLP | | 2019 |
| ATELIER.41 Limited | Professional & scientific | 2014 |
| ATELIER63 Limited | Professional & scientific | 2022 |
| Atem Trading Co Ltd | Professional & scientific | 2024 |
| ATF Accountancy Ltd | Professional & scientific | 2022 |
| ATF Tax Consultancy Ltd | Professional & scientific | 2016 |
| Atfe Ltd | Administrative & support | 2024 |
| Atgt Limited | Professional & scientific | 2024 |
| Athe Limited | Education | 2010 |
| Athena and Soteria Limited | Financial services | 2025 |
| Athena Games Limited | Wholesale & retail | 2013 |
| Athena Service Group Limited | Information & communication | 2021 |
| Athenaai by AOR Ltd | Information & communication | 2025 |
| Athlete Inc Limited | Financial services | 2024 |
| Atholl House Productions Limited | Information & communication | 2007 |
| Athome Lettings Norwich Ltd | Real estate | 2024 |
| Ativar Consulting Ltd | Health & social care | 2024 |
| Atkins Developments Ltd | Construction | 2014 |
| Atkinson Moss Limited | Administrative & support | 2017 |
| Atkinson Professional Services Ltd | Real estate | 2026 |
| Atkinson Smith Digital Ltd | Information & communication | 2025 |
| Atlan Consulting Limited | Professional & scientific | 2020 |
| Atlanta Healthcare Limited | Health & social care | 2004 |
| Atlantic Avenue Cars Limited | Transport & logistics | 2026 |
| Atlantic Bathrooms & Kitchens Limited | Construction | 2003 |
| Atlantic Commercial Finance Limited | Administrative & support | 2024 |
| Atlantic Engineering Group Ltd | Construction | 2017 |
| Atlantic Trading (Norfolk) Limited | Wholesale & retail | 2001 |
| Atlantic Truck and Van Hire Limited | Other services | 2017 |
| Atlantica Residents Limited | Households | 1982 |
| Atlantica Table Ltd | Wholesale & retail | 2019 |
| Atlantis Geoservices Ltd | Professional & scientific | 2021 |
| Atlas (Great Yarmouth) Limited | Real estate | 2003 |
| Atlas AVT Limited | Information & communication | 2024 |
| Atlas Bungalows Management Company Limited | Professional & scientific | 2005 |
| Atlas Food Processing Solutions Limited | Professional & scientific | 2012 |
| ATM Store Ltd | Wholesale & retail | 2021 |
| Atmere Finance Ltd | Financial services | 2026 |
| Atom Content Marketing Ltd | Information & communication | 1993 |
| Atomic 42 Ltd | Financial services | 2022 |
| Atomic Promotions Limited | Professional & scientific | 2022 |
| Atoz Cleaning Ltd | Administrative & support | 2022 |
| ATP Health and Fitness Norwich Limited | Arts & recreation | 2011 |
| Atrium Associates Ltd | Administrative & support | 2019 |
| Atrium Healthcare Ltd | Administrative & support | 2022 |
| Atrium Holdings Group Ltd | Financial services | 2022 |
| Atrium Recruitment Ltd | Administrative & support | 2022 |
| ATS (ALL the Supplies) Limited | Wholesale & retail | 2018 |
| ATS Resellers Ltd | Wholesale & retail | 2026 |
| Attachment Centred Education Solutions Ltd | Education | 2019 |
| Attack Mode Lola Ltd | Professional & scientific | 2015 |
| Attain People Limited | Administrative & support | 2021 |
| Attaintransformation Ltd | Public administration | 2025 |
| Attention to Detail Norfolk Limited | Construction | 2018 |
| Atticus Health UK Ltd | Professional & scientific | 2022 |
| Atticus' Mind Limited | Professional & scientific | 2023 |
| Attleborough Card Shop Ltd | Administrative & support | 2017 |
| Attleborough Travel Ltd | Administrative & support | 2012 |
| Atto Group Holdings Ltd | Professional & scientific | 2014 |
| Attodiagnostics Ltd | Health & social care | 2016 |
| Attodna Limited | Professional & scientific | 2024 |