| A.A.W. Windscreens Ltd | Wholesale & retail | 2000 |
| A.Copp Building Services Ltd | Construction | 2012 |
| A.E.Sams Limited | Real estate | 1934 |
| A.P.M. Management Limited | Construction | 1977 |
| A.S. (Weymouth) Limited | Hospitality | 2008 |
| A.S.K. Piearcey Limited | Professional & scientific | 2006 |
| A1-JETCONSULTING Limited | Professional & scientific | 2022 |
| A2A Consulting Limited | Professional & scientific | 2015 |
| AAA Cars (Southern) Ltd | Transport & logistics | 2015 |
| Aarinkan Ltd | Wholesale & retail | 2026 |
| Abbco Consultancy Limited | Information & communication | 1994 |
| Abbey (Design & Build) Limited | Construction | 2003 |
| Abbey Lodge Limited | Real estate | 2021 |
| Abbeyfield Weymouth Society Limited(The) | Health & social care | 1961 |
| Abbots Court (Weymouth) Limited | Households | 1990 |
| Abbotsbury Software Limited | Information & communication | 1980 |
| Abbott & Rees Funeral Directors Limited | Other services | 2006 |
| ABC 2001 Ltd | Real estate | 2015 |
| ABC Design & Moji UK Ltd | Wholesale & retail | 2023 |
| ABC Holdings & Management Ltd | Financial services | 2021 |
| ABC Plumbing & Heating Limited | Construction | 2007 |
| Abellum Limited | Financial services | 2005 |
| Abington Construction (SW) Limited | Construction | 2014 |
| Absolute ALL Inclusive Care Limited | Health & social care | 2007 |
| Absolute Associates Consulting Ltd | Professional & scientific | 2013 |
| Absolute Building Care Limited | Construction | 2002 |
| ABT Solutions Limited | Other services | 2010 |
| ABW (Dorset) Ltd | Construction | 2019 |
| Account Direct Limited | Professional & scientific | 2005 |
| Ace General Builders Limited | Construction | 2004 |
| Ace Shot Golf Ltd | Arts & recreation | 2025 |
| Achilles Property Holding Limited | Real estate | 2025 |
| ACM Accountants Ltd | Professional & scientific | 2013 |
| Acme Property Limited | Real estate | 2016 |
| Acorn Gardening & Property Services Limited | Administrative & support | 2012 |
| Acqua Beach Limited | Hospitality | 2022 |
| Acrogen Limited | Professional & scientific | 1995 |
| Active Mobility Vehicles Limited | Wholesale & retail | 1996 |
| Active Motoring Services Ltd | Administrative & support | 2011 |
| Acuherbs (TCM) Limited | Other services | 2015 |
| AD Dentistry Ltd | Health & social care | 2025 |
| Adam Billings Building Services Ltd | Construction | 2021 |
| Adam Billings General Builder Limited | Construction | 2019 |
| Adam Burden Carpentry Limited | Administrative & support | 2017 |
| Adaptive Business Management Systems Limited | Information & communication | 2011 |
| Adelaide Court (Weymouth) Limited | Households | 1987 |
| ADL Contractors Limited | Professional & scientific | 2010 |
| ADL Directors Limited | Professional & scientific | 2006 |
| ADL Secretaries Limited | Professional & scientific | 2006 |
| ADM Environmental Services Limited | Water & waste | 2026 |
| Admirals Quarter Management Company Ltd | Households | 2009 |
| ADP Lettings Limited | Real estate | 2026 |
| Adro Systems UK Limited | Manufacturing | 2003 |
| Adverge Limited | Financial services | 2021 |
| Advoco (SW) Limited | Professional & scientific | 2002 |
| Advoco Contractor Umbrella Limited | Professional & scientific | 2017 |
| Advoco Management Limited | Real estate | 2013 |
| Aerworx Limited | Wholesale & retail | 2011 |
| AES Plumbing Ltd | Construction | 2023 |
| Affordable Blinds and Shutters Limited | Construction | 2018 |
| After Dark Agency Ltd | Professional & scientific | 2025 |
| AG Properties Freehold 57 Ltd | Real estate | 2024 |
| Against the Current Ltd | Administrative & support | 2019 |
| Agricultural Welding Services Limited | Other services | 2024 |
| Agriworx Limited | Agriculture & fishing | 2016 |
| Ainslie Aviation Limited | Transport & logistics | 2018 |
| Air Domain Solutions Ltd | Professional & scientific | 2013 |
| Air Fair Ltd | Administrative & support | 2009 |
| Air Support Limited | Professional & scientific | 2024 |
| Airosafe Ltd | Public administration | 2019 |
| AJB Construction Solutions Ltd | Construction | 2008 |
| AJF Security Ltd | Administrative & support | 2016 |
| AJL Property Management Ltd | Real estate | 2025 |
| Ajoo.Co Ltd | Wholesale & retail | 2025 |
| Alacrity Aviation Limited | Professional & scientific | 2017 |
| Albany Accommodation Ltd | Hospitality | 2017 |
| Albion Mercer Limited | Professional & scientific | 2026 |
| Albion Property Services Limited | Real estate | 2016 |
| Albion Robotics Limited | Transport & logistics | 1987 |
| Aledanic Limited | Hospitality | 2022 |
| Alex Stage Ltd | Professional & scientific | 2025 |
| Alexandra Care Limited | Professional & scientific | 2013 |
| Alexandra Court (Weymouth) Management Co. Limited | Households | 1973 |
| Alf's Weymouth Limited | Hospitality | 2015 |
| Alfamax Catering Services Limited | Manufacturing | 2010 |
| Alison Stockton Ltd | Health & social care | 2023 |
| ALL Things Tasty Ltd | Hospitality | 2018 |
| All-Engineering Inspection Services Ltd | Professional & scientific | 2025 |
| Allberry Gardens Limited | Households | 1996 |
| Allen Building & Landscaping Ltd | Administrative & support | 2018 |
| Allfloors Dorset Limited | Construction | 2021 |
| Allied Printing Ltd | Wholesale & retail | 2025 |
| Allways Removals Limited | Transport & logistics | 1951 |
| ALM Place Management Company Limited | Households | 2014 |
| ALM Vehicle Sales Limited | Wholesale & retail | 2012 |
| Alnat Limited | Professional & scientific | 2006 |
| Alpha Windows Portland Ltd | Construction | 2023 |
| Alpine Winter Sports Ltd | Administrative & support | 2022 |
| Altar Apparel Ltd | Wholesale & retail | 2023 |
| Altogether Care - Care at Home (UK) LLP | | 2011 |