| A.R. Leisure Park Installations Limited | Construction | 2013 |
| A.S Installs Ltd | Construction | 2015 |
| A.W. Fabrications Limited | Manufacturing | 2001 |
| A1 Fabrications & Engineering Limited | Manufacturing | 2008 |
| A2 Construction Ltd | Construction | 2020 |
| A6 Business Centre 11 Limited | Real estate | 2020 |
| A6 Business Centre 3 Limited | Real estate | 2020 |
| AA Super Food Services Limited | Hospitality | 2022 |
| AA Waste Services Northampton Ltd | Water & waste | 2025 |
| AAA Clothing Limited | Administrative & support | 2016 |
| AAA Services (Northants) Limited | Wholesale & retail | 2015 |
| Aaaskk Finance Limited | Other services | 2018 |
| AAG Consultancy Services Ltd | Professional & scientific | 2019 |
| AAG Services Ltd | Construction | 2018 |
| Aaham Ltd | Hospitality | 2023 |
| Aaham Welly Ltd | Hospitality | 2025 |
| Aapex Cars Limited | Transport & logistics | 2026 |
| AB - AZ Enterprises Ltd | Hospitality | 2024 |
| AB Construct Ltd | Construction | 2018 |
| AB Expedition Ltd | Transport & logistics | 2025 |
| AB Johnson Services Limited | Other services | 2016 |
| AB Properties & Lettings Ltd | Real estate | 2025 |
| AB Property Services (Thenford Street) Limited | Households | 2010 |
| AB Recovery and Breakdown Ltd | Wholesale & retail | 2025 |
| AB Starr Properties Limited | Real estate | 2022 |
| Ab&C Transport Ltd | Transport & logistics | 2018 |
| Abacus Fairhomes Ltd | Real estate | 2020 |
| Abbots Rental Ltd | Administrative & support | 2025 |
| Abbott Signs (Northampton) Limited | Manufacturing | 2007 |
| Abbotts Amusements Limited | Other services | 1949 |
| Abegail Ltd | Health & social care | 2021 |
| Ability Training Limited | Professional & scientific | 1997 |
| Able Assist Limited | Wholesale & retail | 2017 |
| Able Motor Services Limited | Wholesale & retail | 2021 |
| Abrams Building and Carpentry Limited | Construction | 2017 |
| Absolute Drainage Services Limited | Administrative & support | 2003 |
| Absolute Energy Systems Limited | Construction | 2023 |
| Abstract Worlds Limited | Information & communication | 1998 |
| ACA Engineering Ltd | Manufacturing | 2025 |
| Academy Library Supplies Limited | | 1984 |
| Accounts Back Office Support Ltd | Professional & scientific | 2018 |
| Accurate Assessment UK Ltd | Information & communication | 2023 |
| Accurl UK Ltd | Manufacturing | 2018 |
| Ace 88 Ltd | Information & communication | 2015 |
| Ace DRY Lining (Northants) Limited | Construction | 2016 |
| Ace Ecology Ltd | Professional & scientific | 2025 |
| Ace GB Holdings Limited | Administrative & support | 2017 |
| Ace GB Investments Limited | Administrative & support | 2017 |
| Ace Mini Skip Hire Ltd | Water & waste | 2025 |
| Ace Pro Security Services Ltd | Administrative & support | 2025 |
| Ace Roof Services Ltd | Construction | 2023 |
| Achempim Limited | Transport & logistics | 2017 |
| Achievers Educational Support Services Limited | Public administration | 2024 |
| Acipiter Limited | Real estate | 2018 |
| Acko Beach Property Services Limited | Construction | 2019 |
| ACL & Co Ltd | Construction | 2013 |
| ACM Garage Doors Ltd | Construction | 2025 |
| Acomtec Ltd | Professional & scientific | 1998 |
| Acorn Aluminium Group Holdings Ltd | Financial services | 2005 |
| Acorn Aluminium Holdings Limited | Financial services | 2005 |
| Acrigab Ltd | Transport & logistics | 2013 |
| Actio Consulting UK Limited | Professional & scientific | 2013 |
| Action 2 Care Ltd | Health & social care | 2015 |
| Active Automotive Limited | Wholesale & retail | 2007 |
| Active Pet Physio Ltd | Professional & scientific | 2010 |
| Activeozone Limited | Professional & scientific | 2017 |
| Activeozone Properties Limited | Real estate | 2021 |
| Actus Performance Ltd | Wholesale & retail | 2017 |
| ACY Construction Ltd | Construction | 2021 |
| ACY KOI Ltd | Extraterritorial | 2021 |
| AD & DS Construction Limited | Construction | 2024 |
| AD Aggregator Platform Limited | Financial services | 2015 |
| AD Keplin Investments Ltd | Real estate | 2023 |
| ADA Cleaning Solutions Ltd | Administrative & support | 2025 |
| Ada&G Limited | Construction | 2020 |
| Adair Technical Ltd | Information & communication | 2020 |
| Adam's Property Restoration Limited | Construction | 2017 |
| Adams & Associates Developments Ltd | Real estate | 2019 |
| Adams & Associates Ltd | Financial services | 2004 |
| Adams & Associates Property Division Ltd | Administrative & support | 2017 |
| Adams Smith Consulting Limited | Professional & scientific | 2006 |
| ADC Online Limited | Information & communication | 2004 |
| ADC Surv Ltd | Professional & scientific | 2022 |
| ADD Commercials Limited | Information & communication | 2013 |
| Addai Ltd | Administrative & support | 2015 |
| Addiel Healthcare Limited | Health & social care | 2012 |
| Adept Pure Water Limited | Water & waste | 2003 |
| Adhj Limited | Health & social care | 2024 |
| ADI Landscaping Services Ltd | Administrative & support | 2022 |
| Adigaa Ltd | Wholesale & retail | 2026 |
| Adimax Ltd | Construction | 2025 |
| ADJ Architectural Services Limited | Professional & scientific | 2012 |
| Admarmi Properties Ltd | Real estate | 2023 |
| Adnama Limited | Professional & scientific | 2020 |
| Adonai Salvation Ministries Limited | Other services | 2016 |
| Adrah Studios Ltd | Professional & scientific | 2020 |
| Adriel Property Management Limited | Financial services | 2024 |
| Advanced Fabrication (Wellingborough) Limited | Manufacturing | 2022 |
| Advanced Inspection Services Limited | Other services | 1998 |
| Advanced Switching Solutions Limited | Professional & scientific | 2016 |