| Acts 435 | Health & social care | 2009 |
| Acuherbs Clinic Limited | Health & social care | 2023 |
| AD Advisory Ltd | Professional & scientific | 2017 |
| AD Astra (Broadening Horizons) Limited | Education | 2015 |
| AD Power Consultancy Services Ltd | Professional & scientific | 2025 |
| AD Signal Limited | Information & communication | 2018 |
| AD Welding Services Ltd | Manufacturing | 2023 |
| Ad-In Media Limited | Information & communication | 2026 |
| ADA Pizza Ltd | Hospitality | 2024 |
| ADA York Ltd | Other services | 2023 |
| Adam Herrington Property Developments Ltd | Administrative & support | 2025 |
| Adam Wiles Plumbing & Tiling Ltd | Construction | 2021 |
| Adams & Co Property Holdings Ltd | Real estate | 2022 |
| Adaptive Creations Limited | Information & communication | 2018 |
| Adara Tattoo Collective Ltd | Arts & recreation | 2016 |
| Adders of Fact Limited | Transport & logistics | 2014 |
| Addinall Interiors Limited | Manufacturing | 2019 |
| Addison Green Limited | Water & waste | 2012 |
| Addison's Limited | Real estate | 1983 |
| Adduco Ltd | Professional & scientific | 2012 |
| Adelaide Clinic Limited | Extraterritorial | 2010 |
| Adelphi Properties (York) Ltd | Real estate | 2025 |
| ADF Properties Limited | Real estate | 1998 |
| Adhurst Developments Limited | Real estate | 1997 |
| Adico Ltd | Construction | 2022 |
| Adiuvo Limited | Professional & scientific | 2004 |
| Adjusted Music Limited | Information & communication | 2005 |
| Adkins Design Ltd | Administrative & support | 2003 |
| ADM Services (UK) Ltd | Public administration | 2005 |
| Administration Services Limited | Administrative & support | 1988 |
| Adnfc Financial Consultants Ltd | Financial services | 2019 |
| Adnfc Legal Services Ltd | Professional & scientific | 2022 |
| Adnfc Wealth Management Ltd | Professional & scientific | 2024 |
| Adolescent Care Team Ltd. | Health & social care | 2019 |
| Adora Regal Limited | Professional & scientific | 2022 |
| Adrian Flint Plastering and Rendering Services Ltd | Construction | 2026 |
| Adrian Pierce Business Development Ltd | Arts & recreation | 2015 |
| ADS Scaffolding (York) Limited | Construction | 2012 |
| Adsb Consulting Limited | Public administration | 2019 |
| Adsonce Ltd | Information & communication | 2021 |
| Adtran Networks (UK) Limited | Manufacturing | 1998 |
| Adult Autism Assessments Limited | Health & social care | 2024 |
| Adult Development (UK) Ltd | Education | 2017 |
| Advance HE | Education | 2003 |
| Advance Hindsight Limited | Professional & scientific | 2019 |
| Advance Rail Ltd | Education | 2024 |
| Advanced Alloy Services Limited | Water & waste | 1993 |
| Advanced Alloys Group Limited | Financial services | 2019 |
| Advanced Artist Training Ltd | Professional & scientific | 2025 |
| Advanced Electrical Services York Ltd | Construction | 2010 |
| Advanced Health & Wellness Ltd | Health & social care | 2024 |
| Advanced Inheritance Limited | Financial services | 2023 |
| Advanced Muscular Integration Technique (York) Limited | Real estate | 2024 |
| Advanced Painters of Dulwich Luxury Finishes Limited | Construction | 2023 |
| Advanced Parking Tech Ltd | Information & communication | 2020 |
| Advanced Plumbing and Heating Engineers Ltd | Construction | 2026 |
| Advanced Roofing Contractors Ltd | Construction | 2023 |
| Advanced Selling Skills Academy Limited | Administrative & support | 2002 |
| Advancia Consulting Group Ltd | Professional & scientific | 2026 |
| Advantage Consulting Limited | Professional & scientific | 2022 |
| Advent Accountants Ltd | Professional & scientific | 2024 |
| Advent Search Partners LLP | | 2015 |
| Adventure Brands Ltd | Manufacturing | 2018 |
| Adventure Getaways Ltd | Administrative & support | 2025 |
| Adventure Mobility Group Ltd | Wholesale & retail | 2024 |
| Adventure Rails Ltd | Professional & scientific | 2022 |
| Adventurers Day Nursery Ltd | Education | 2020 |
| Adversify Ltd | Information & communication | 2022 |
| Adverte Media Group Ltd | Information & communication | 2026 |
| Advertising Management Limited | Professional & scientific | 2006 |
| Advin SPV1 Limited | Financial services | 2024 |
| Adviserhome Limited | Financial services | 2011 |
| ADW Enterprises Limited | Real estate | 2015 |
| Ady's Motors York Ltd | Wholesale & retail | 2025 |
| Adytailing Ltd | Administrative & support | 2023 |
| AE Fitness Ltd | Other services | 2024 |
| AEC Solar Division Ltd | Construction | 2024 |
| AEF (Malton) Limited | Financial services | 2011 |
| AEG (York) Ltd | Manufacturing | 2013 |
| AEM Construction Limited | Construction | 2014 |
| AER8 Marketing Limited | Professional & scientific | 2011 |
| Aerial Gymnastics York Ltd | Arts & recreation | 2025 |
| Aero Contracting Limited | Manufacturing | 2014 |
| Aeronex International Limited | Professional & scientific | 2026 |
| Aerostar Technologies Limited | Extraterritorial | 2025 |
| AES York Limited | Wholesale & retail | 2015 |
| Aesthetica Magazine Limited | Information & communication | 2006 |
| Aesthetics by Carrieanne Ltd | Other services | 2025 |
| Aesthetics Services Ltd | Professional & scientific | 2022 |
| AEW Wind Limited | Energy | 2025 |
| AFA Consulting Engineers Ltd | Professional & scientific | 2023 |
| Affordable Cars (Yorkshire) Limited | Wholesale & retail | 2013 |
| Affordable Homes to LET Limited | Real estate | 2019 |
| Affordable Plumbing & Heating Services (York) Ltd | Construction | 2017 |
| Affps Ltd | Health & social care | 2025 |
| Afmw Ltd | Health & social care | 2020 |
| Afon Limited | Administrative & support | 2016 |
| Afron Limited | Professional & scientific | 2008 |
| Afshan Optometry Ltd | Health & social care | 2014 |
| After Hours Bakery Ltd | Manufacturing | 2026 |