| A.D.V. Communications Limited | Information & communication | 1992 |
| A.G. Standard Company Limited | Extraterritorial | 1929 |
| A.L.S 1ST AID Training Ltd | Education | 2022 |
| A.R Business Consultancy Limited | Professional & scientific | 2004 |
| A.R.B Agri Fencing Specialist Ltd | Agriculture & fishing | 2017 |
| A.R.M Road Haulage Ltd | Transport & logistics | 2022 |
| A.S.L. Hida Valeting Limited | Other services | 2013 |
| A.T Car Sales Limited | Wholesale & retail | 2012 |
| A.T. Saunders & SON Limited | Construction | 2010 |
| A.T.P. Instrumentation Ltd. | Manufacturing | 1990 |
| A.V. Garage Ltd | Wholesale & retail | 2025 |
| A1 Service Expert Ltd | Wholesale & retail | 2022 |
| A1 Skip Hire Northampton Limited | Extraterritorial | 2021 |
| A14 Supplies Ltd | Wholesale & retail | 2018 |
| A2Z Office Supplies Ltd | Other services | 2019 |
| A2Z Unique Developments Ltd | Construction | 2018 |
| A3J Group Limited | Financial services | 2020 |
| A3J Limited | Financial services | 2019 |
| A6 Accounting Limited | Professional & scientific | 2014 |
| A6 Mouldings Limited | Manufacturing | 2005 |
| AA Nexus Ltd | Wholesale & retail | 2026 |
| AA Thornton Limited | Wholesale & retail | 2005 |
| AAA Innovations Limited | Wholesale & retail | 2024 |
| Aapleghar Limited | Real estate | 2021 |
| AB Beauty & Hair Ltd | Other services | 2024 |
| AB Diagnostics Ltd | Health & social care | 2025 |
| AB Fusion and Groundworks Limited | Construction | 2019 |
| AB Web Holdings Ltd | Information & communication | 2000 |
| Abbey Builders (Kettering) Limited | Construction | 2013 |
| Abbey Damp Proofing & Timber Preservations Ltd | Construction | 2023 |
| Abbott Rose Consulting Ltd | Professional & scientific | 2018 |
| ABC Coding Limited | Manufacturing | 2010 |
| ABC Sklep Limited | Wholesale & retail | 2024 |
| ABI Cookman Property Ltd | Real estate | 2022 |
| Abin Jose Ltd | Information & communication | 2023 |
| Abington Properties Limited | Real estate | 2006 |
| Abishot Mouldings Ltd | Manufacturing | 1996 |
| ABL Innovations Ltd | Professional & scientific | 2023 |
| Able Taxi Kettering Ltd | Transport & logistics | 2018 |
| Abmat Ltd | Real estate | 2019 |
| Abovo Group Limited | Professional & scientific | 2019 |
| Abraham Axis Properties Ltd | Real estate | 2024 |
| Abraham Delroy Phillips Ltd | Extraterritorial | 2022 |
| Abraham Health Care Limited | Health & social care | 2017 |
| Absimplytextile Ltd | Wholesale & retail | 2022 |
| Absolute Clean 'N' Clear Ltd | Construction | 2014 |
| Absolute Clearance & Cleaning Ltd | Water & waste | 2025 |
| Absolute FLOORS247 Ltd | Construction | 2026 |
| AC Groundworks Construction Limited | Wholesale & retail | 2017 |
| AC Vacuum Excavation Ltd | Construction | 2025 |
| Academyfd Ltd | Professional & scientific | 2024 |
| Acanthus Management Limited | Administrative & support | 2009 |
| Accelerated Play Limited | Hospitality | 2025 |
| Access Floor Systems Limited | Extraterritorial | 1973 |
| Access Global Ltd | Administrative & support | 2019 |
| Access Security Cards Limited | Administrative & support | 2013 |
| Accident Helpline Limited | Professional & scientific | 1997 |
| Accommodation Concern | Information & communication | 2012 |
| Accommodation Cumbria Ltd | Real estate | 2023 |
| Accommodation Finders Limited | Hospitality | 2023 |
| Ace BLS Limited | Education | 2013 |
| Ace Domestics (Kettering) Limited | Wholesale & retail | 2008 |
| Ace House Clearance Limited | Wholesale & retail | 2008 |
| Ace Marketplace Ltd | Extraterritorial | 2024 |
| Ace Reuse (Brixworth) Limited | Other services | 2010 |
| Ace Reuse (Wellingborough) Limited | Other services | 2017 |
| Ace Reuse Limited | Water & waste | 2010 |
| Ace Reuse Recycling Ltd | Water & waste | 2022 |
| Ace Scrap Limited | Water & waste | 2022 |
| Acedrone UK Ltd | Professional & scientific | 2025 |
| Aces Kettering Ltd | Hospitality | 2026 |
| Achak Limited | Financial services | 2019 |
| Achfra Enterprise Limited | Wholesale & retail | 2021 |
| Achintyah Limited | Health & social care | 2019 |
| ACL Group Ltd | Construction | 2020 |
| Acorn Seating Ltd | Manufacturing | 2019 |
| Acosmetics Clinic Ltd | Other services | 2021 |
| Acosmetics Training Ltd | Education | 2024 |
| ACS Trading Ltd | Households | 2025 |
| Activate Northants Ltd | Health & social care | 2023 |
| Active Installations Limited | Professional & scientific | 2016 |
| Active Progression Limited | Information & communication | 1999 |
| Active Support Service Limited | Education | 2008 |
| Activheat (UK) Limited | Construction | 2007 |
| Actreg (U.K.) Limited | Wholesale & retail | 1990 |
| ACW Property Investments Ltd | Real estate | 2020 |
| AD & JG Holdings Limited | Financial services | 2021 |
| Adai Digital Ltd | Information & communication | 2026 |
| Adam Morris Services Ltd | Transport & logistics | 2023 |
| Adamczyk Property Investments Ltd | Real estate | 2026 |
| Adavea Limited | Real estate | 2026 |
| ADDING2IT Limited | Administrative & support | 2005 |
| Addo & Addo Limited | Administrative & support | 2022 |
| Adenike Healthcare Limited | Health & social care | 2025 |
| Aditi Data Solutions Limited | Information & communication | 2024 |
| ADL General Haulage Limited | Transport & logistics | 2018 |
| ADN Electrical Ltd | Construction | 2025 |
| Adonai Enterprise Ltd | Health & social care | 2019 |
| Adraho Ltd | Information & communication | 2025 |
| Adrian Fytche Furniture Sales Limited | Wholesale & retail | 2013 |