| Almaya Care Support Ltd | Public administration | 2025 |
| Almegard Consulting Ltd | Professional & scientific | 2023 |
| Almey Roofing Services Ltd | Construction | 2022 |
| Almost Ltd | Information & communication | 2020 |
| Alnc Property Investment Limited | Real estate | 2017 |
| Alockey Ltd | Real estate | 2025 |
| Alokozay Transport Ltd | Transport & logistics | 2020 |
| Aloma.Io Ltd | Information & communication | 2022 |
| Alone Wolf Ltd | Wholesale & retail | 2025 |
| Alpaka Ltd | Information & communication | 2016 |
| Alpha & Omega (UK) Limited | Real estate | 2005 |
| Alpha 2994 Limited | Construction | 2013 |
| Alpha Art Trades Ltd | Arts & recreation | 2024 |
| Alpha Barbers & Omega Hairdressing Limited | Other services | 2022 |
| Alpha Command Protection Ltd | Administrative & support | 2025 |
| Alpha Contracts Leasing Limited | Wholesale & retail | 1998 |
| Alpha Design and Build Northampton Ltd | Construction | 2021 |
| Alpha DRY Cleaning Solutions Ltd | Other services | 2023 |
| Alpha Energy Consulting Limited | Professional & scientific | 2014 |
| Alpha Gynaecology Ultrasound Limited | Health & social care | 2018 |
| Alpha Industrial Supplies Limited | Wholesale & retail | 2024 |
| Alpha Infotech Services Ltd | Information & communication | 2015 |
| Alpha Live Limited | Administrative & support | 2017 |
| Alpha Male Aesthetics Limited | Other services | 2023 |
| Alpha Omega Consulting Limited | Information & communication | 2008 |
| Alpha Omega Investments & Holdings Ltd | Wholesale & retail | 2021 |
| Alpha Pallets Limited | Manufacturing | 2012 |
| Alpha Performance Fabrication Limited | Manufacturing | 2018 |
| Alpha Pharmaceuticals Pharma Ltd | Wholesale & retail | 2025 |
| Alpha Pilers Limited | Construction | 2016 |
| Alpha Pro Cleaners Ltd | Administrative & support | 2023 |
| Alpha Services (Northampton) Limited | Construction | 2015 |
| Alpha Shelf Limited | Wholesale & retail | 2024 |
| Alpha Sports Management Limited | Arts & recreation | 2019 |
| Alpha Technology (INT) Ltd | Professional & scientific | 2013 |
| ALPHA25 Cars and Minibuses Ltd | Transport & logistics | 2014 |
| ALPHA8EXTERNALCLEANING Ltd | Administrative & support | 2026 |
| Alphaarc Ltd | Wholesale & retail | 2026 |
| Alphabet House Day Nurseries Limited | Health & social care | 2003 |
| Alphacare Limited | Education | 1985 |
| Alphagen Projects Limited | Energy | 2014 |
| Alphagen Renewables Limited | Energy | 2011 |
| Alphaset Limited | Manufacturing | 2014 |
| Alpher Amie Ltd | Hospitality | 2018 |
| Alphion Properties Ltd | Real estate | 2026 |
| Alpine Property Management and Consultancy Services Limited | Real estate | 2021 |
| Alpine Scaffolding Ltd | Construction | 2020 |
| Alps Driving School Ltd | Education | 2022 |
| Alps Motors Ltd | Wholesale & retail | 2024 |
| Alrouba Ltd | Real estate | 2020 |
| ALS Bricks Ltd | Wholesale & retail | 2026 |
| ALS Fencing Ltd | Administrative & support | 2010 |
| ALT Approach Ltd | Professional & scientific | 2020 |
| Altamaris Frontier Limited | Mining & quarrying | 2025 |
| Altavia HTT Limited | Information & communication | 2003 |
| Altavia UK Group Limited | Professional & scientific | 1990 |
| Altay Ural Limited | Hospitality | 2021 |
| Alterego Creative Solutions Ltd | Arts & recreation | 2012 |
| Alternative Spectrum Consultancy Services Limited | Professional & scientific | 2026 |
| Althorp Enterprises Partnership LP | | 2012 |
| Althorp Farms Limited | Agriculture & fishing | 2015 |
| Althorp Nominee One Limited | Extraterritorial | 2013 |
| Althorp Nominee Two Limited | Extraterritorial | 2013 |
| Altimo Ltd | Hospitality | 2025 |
| Altitude-Recruitment Limited | Administrative & support | 2014 |
| Altius PT Limited | Arts & recreation | 2018 |
| Altius Research Ltd | Wholesale & retail | 2026 |
| Alto Holdings Limited | Other services | 2019 |
| Altomax Services Ltd | Health & social care | 2019 |
| Altona Ltd | Information & communication | 2022 |
| Altrise Recruitment Ltd | Administrative & support | 2026 |
| Altunatmaz Fish Ltd | Hospitality | 2020 |
| Altura Distribution Ltd | Administrative & support | 2026 |
| Altura Service Limited | Wholesale & retail | 2016 |
| Alu-Plas Windows and Doors Limited | Construction | 1999 |
| Aluminium Contracts Limited | Manufacturing | 1999 |
| Alutec Rainwater Systems Limited | Manufacturing | 2026 |
| Alvedius Ltd | Financial services | 2015 |
| Alvera Transport Ltd | Transport & logistics | 2021 |
| Alverdiscott 10 Renewables Holdco Ltd | Professional & scientific | 2023 |
| Alverdiscott 10 Renewables Ltd | Administrative & support | 2023 |
| Alverita Properties Ltd | Real estate | 2023 |
| Alvyt Logistics Limited | Transport & logistics | 2026 |
| ALW Virtual PA Services Ltd | Administrative & support | 2026 |
| Always on Cabs Limited | Transport & logistics | 2024 |
| Always Well Ltd | Wholesale & retail | 2016 |
| ALY Barbu Ltd | Hospitality | 2017 |
| Alyks & Co Ltd | Administrative & support | 2018 |
| Alyman Ltd | Construction | 2020 |
| Alynom Limited | Health & social care | 2018 |
| Alyshas Beauty Ltd | Other services | 2023 |
| AM Accounting & Tax Solutions Ltd | Professional & scientific | 2025 |
| AM Aesthetics Ltd | Other services | 2012 |
| AM Engineering (Kettering) Ltd | Wholesale & retail | 2026 |
| AM Facilities Management Ltd | Hospitality | 2011 |
| AM Plant Limited | Administrative & support | 2022 |
| AM Portfolio Ltd | Real estate | 2021 |
| AM Property and Investments Ltd | Real estate | 2021 |
| AM Vans Ltd | Transport & logistics | 2025 |
| AMA Northampton Hair Ltd | Other services | 2026 |