| Abavia Training Ltd | Education | 2025 |
| Abbas Ecology Limited | Professional & scientific | 2012 |
| Abbas GAS Services Limited | Construction | 2001 |
| Abbey Hearing Clinics Ltd | Wholesale & retail | 2010 |
| Abbotsbury Holdings Ltd | Wholesale & retail | 2023 |
| Abbotsbury Tourism Limited | Arts & recreation | 1999 |
| Abfield Limited | Professional & scientific | 1992 |
| Ablecity Limited | Other services | 1987 |
| ABM Building Solutions Ltd | Information & communication | 2005 |
| Acacia Developments Limited | Real estate | 2016 |
| Acacia Investing Limited | Extraterritorial | 2020 |
| Access ALL Areas South West Limited | Administrative & support | 2015 |
| Access Cleaning Contractors Limited | Administrative & support | 2023 |
| Accessibleprs Ltd | Professional & scientific | 2020 |
| Accommodatingu.Com Ltd | Real estate | 2013 |
| Accordant Marketing UK Ltd | Wholesale & retail | 2006 |
| Ace Your Life Coaching Ltd | Public administration | 2024 |
| ACH Consultancy Ltd | Arts & recreation | 2019 |
| Acland Park Management Co. Limited | Households | 2016 |
| Acorn Builders (Dorset) Limited | Construction | 2002 |
| Acorn Conservatories Limited | Construction | 1998 |
| Acoustic Edge Ltd | Professional & scientific | 2023 |
| Action Annabel Stunts Limited | Arts & recreation | 2019 |
| Activate Performing Arts | Arts & recreation | 1997 |
| AD Valorem Consulting (UK) Limited | Professional & scientific | 2005 |
| Adams Garage (Dorchester) Ltd | Wholesale & retail | 2017 |
| Addison Capital Limited | Financial services | 2014 |
| Addison Developments Four Limited | Real estate | 2016 |
| Addison Developments Limited | Construction | 1997 |
| Addison Developments One Limited | Professional & scientific | 2007 |
| Addison Developments Three Limited | Real estate | 2011 |
| Addison Developments Two Limited | Professional & scientific | 2007 |
| ADK Hire & Sales Ltd | Administrative & support | 2024 |
| Admazing Limited | Professional & scientific | 2021 |
| Admecs Healthcare Limited | Real estate | 2017 |
| Adrian Jones Associates Limited | Professional & scientific | 2010 |
| Advanced Investigation Systems Limited | Construction | 2006 |
| Advantage Digital Print Limited | Manufacturing | 2014 |
| Advantage Wellbeing Ltd | Health & social care | 2021 |
| Aegis Advisory Ltd | Information & communication | 2024 |
| AEL Property Management Ltd | Real estate | 2014 |
| Aero Team Model Distribution Ltd. | Extraterritorial | 2014 |
| Aero X Europe Ltd | Professional & scientific | 2025 |
| Aesthetics on the Square Ltd | Other services | 2024 |
| AF Curtis Ltd | Manufacturing | 2022 |
| Affiliate Insider Limited | Information & communication | 2017 |
| Afzal Urology Ltd | Health & social care | 2007 |
| AG (Dorset) Ltd | Education | 2021 |
| AG Esports Consulting Limited | Arts & recreation | 2019 |
| AG Industrial Safety & Controls Ltd | Professional & scientific | 2024 |
| Agaman Limited | Extraterritorial | 2016 |
| AGE Concern in Dorset Limited | Health & social care | 2008 |
| AGE UK Dorchester | Health & social care | 2011 |
| AGE UK Dorset Enterprises Limited | Health & social care | 2016 |
| Agnc Event Management Ltd | Arts & recreation | 2024 |
| Agnew Investments Limited | Hospitality | 1961 |
| Agritas Group Ltd | Financial services | 2019 |
| Agritas UK Ltd | Construction | 2019 |
| AGV Retail Limited | Manufacturing | 2011 |
| Agvanced Grain Systems Limited | Agriculture & fishing | 2021 |
| Agvanced Installations Limited | Construction | 2000 |
| Agvanced UK Limited | Financial services | 2021 |
| Ah-Dermatology Ltd | Health & social care | 2024 |
| Ah-Prop Ltd | Real estate | 2024 |
| AI.INFIN8 Ltd | Information & communication | 2024 |
| Aimms OIL and GAS Services Ltd | Professional & scientific | 2022 |
| Air Broadcasting Ltd | Information & communication | 2025 |
| Air FM Community Interest Company | Information & communication | 2012 |
| Air Pelagic Ltd | Administrative & support | 2009 |
| Aira Business Solutions Limited | Professional & scientific | 2015 |
| Aircraft Trading U.K. Limited | Administrative & support | 2000 |
| Aitann & Co. Ltd | Wholesale & retail | 2022 |
| AJC Landscape Consultancy Ltd | Professional & scientific | 2020 |
| AJM Sports Limited | Education | 2024 |
| Akhurst Plumbing & Heating Limited | Construction | 2018 |
| AKI Limited | Construction | 2002 |
| AKL Fishing Limited | Administrative & support | 2015 |
| AL Davies Consulting Services Limited | Other services | 2020 |
| AL Molo Limited | Hospitality | 2022 |
| ALA88 Ltd | Health & social care | 2020 |
| ALAA1988 Ltd | Health & social care | 2025 |
| Alacrify Foundation CIC | Information & communication | 2019 |
| Alacrify Ltd | Information & communication | 2005 |
| ALB Plumbing and Heating Services Limited | Construction | 2016 |
| Alderton Estates Limited | Construction | 2026 |
| Alfred Road 1972 Limited | Extraterritorial | 2014 |
| ALI Tabrez Limited | Health & social care | 2020 |
| Alicia Grimes Ltd | Professional & scientific | 2025 |
| Aligned Performance Limited | Arts & recreation | 2012 |
| Alive Chiropractic Ltd | Health & social care | 2021 |
| ALL About Chimneys Limited | Administrative & support | 2014 |
| ALL Aspects Signal Sighting Limited | Professional & scientific | 2024 |
| ALL Things Product Limited | Professional & scientific | 2019 |
| ALL Things Property Limited | Real estate | 2018 |
| Allen & York (Contract) Ltd. | Administrative & support | 2018 |
| Allen & York (Professional & Technical) Ltd. | Administrative & support | 2018 |
| Allen & York Ltd. | Administrative & support | 2018 |
| Alma Berrow Ltd | Arts & recreation | 2020 |
| Almat Construction Limited | Construction | 2020 |
| Almaz Executive Search Limited | Administrative & support | 2023 |