| AAM Solutions Ltd | Information & communication | 2025 |
| Aaron Associates (UK) Limited | Professional & scientific | 2004 |
| Aaron Associates Limited | Real estate | 2013 |
| Aaron Francis Ltd | Administrative & support | 2021 |
| Aaron S J Veness Limited | Information & communication | 2023 |
| Aarvee Hasumi Properties Ltd | Households | 2025 |
| AAS Consult Limited | Professional & scientific | 2012 |
| AB Households UK Limited | Wholesale & retail | 2014 |
| AB RC Construction Ltd | Construction | 2020 |
| AB Tax Solutions Ltd | Professional & scientific | 2026 |
| AB Transport Service Limited | Transport & logistics | 2014 |
| Abalone Waves Ltd | Health & social care | 2026 |
| Abby MUA Ltd | Administrative & support | 2017 |
| ABC Domos Limited | Real estate | 2021 |
| ABC Headhunters Limited | Administrative & support | 2017 |
| ABC Pre-School Beddington LLP | | 2016 |
| Abeey Tech Ltd | Information & communication | 2016 |
| Ability Check Ltd | Administrative & support | 2021 |
| Able Pro Care Solutions Ltd | Health & social care | 2017 |
| Ablemarsh Safety Consultants Ltd | Professional & scientific | 2014 |
| Abraham and Sons Motors Limited | Wholesale & retail | 2018 |
| Abraham and Sons Surrey Ltd | Real estate | 2015 |
| Abundant R Ltd | Administrative & support | 2020 |
| Academic and Professional Research Centre of Britain | Professional & scientific | 2006 |
| Acclaimed Property Services Limited | Construction | 2013 |
| Accountancy N Tax Services Ltd | Professional & scientific | 2015 |
| Accountax Advisory Ltd | Professional & scientific | 2026 |
| Accurate Estimates Limited | Wholesale & retail | 2022 |
| Accutax Accountants Ltd | Professional & scientific | 2017 |
| Ace Interiors Ltd | Construction | 2017 |
| Acenis Ltd | Wholesale & retail | 2020 |
| Acerta Holdings Limited | Professional & scientific | 2014 |
| ACF Auditing Services Limited | Professional & scientific | 2009 |
| Achieve Tutoring Limited | Education | 2019 |
| Aclr & Daughters Ltd | Public administration | 2024 |
| ACM Sparks Services Ltd | Other services | 2014 |
| Acorn Environmental UK Limited | Administrative & support | 1984 |
| Acorn Janitorial Supplies Limited | Extraterritorial | 2009 |
| Acorn Placements Ltd | Administrative & support | 2025 |
| Acquico Holdings Limited | Financial services | 2023 |
| Acta Medical Limited | Administrative & support | 2020 |
| Activefx Limited | Information & communication | 2013 |
| Actors House Property Ltd | Real estate | 2023 |
| ADA Scaffolding Ltd | Construction | 2024 |
| Adamantine Limited | Professional & scientific | 2016 |
| Adana&Istanbul Ltd | Hospitality | 2025 |
| Adaptbuilds Ltd | Construction | 2025 |
| Adastra Operating Limited | Other services | 2017 |
| ADC Healthcare Limited | Manufacturing | 2015 |
| Additive Sustainability Limited | Professional & scientific | 2025 |
| Adentic Ltd | Professional & scientific | 2025 |
| Adepa Enterprises Ltd | Wholesale & retail | 2011 |
| Adhu Idhu Ltd | Information & communication | 2022 |
| Advanced Boardroom Excellence Limited | Professional & scientific | 2013 |
| Aeri (UK) Ltd | Wholesale & retail | 2012 |
| Aerolatino Fitness UK Ltd | Arts & recreation | 2013 |
| Affinity Food Services Ltd | Hospitality | 2026 |
| Aflar Investments Ltd | Real estate | 2023 |
| AFN Technology Limited | Information & communication | 1999 |
| Africa Calling Travel Ltd | Administrative & support | 2021 |
| Africa Felix Consulting Ltd | Professional & scientific | 2015 |
| Africa Shining Limited | Professional & scientific | 2016 |
| Afrinomica Ltd | Other services | 2009 |
| AG Medics Services Limited | Health & social care | 2016 |
| AG Property Investments Holdings Ltd | Real estate | 2025 |
| Agaram Home Ltd | Real estate | 2021 |
| AGB Life Coaching Ltd | Education | 2022 |
| AGE of Essence Larp Ltd | Arts & recreation | 2024 |
| AGG Manual Therapy Ltd | Health & social care | 2020 |
| Agile Management Services Ltd | Wholesale & retail | 2016 |
| Agile Testing Ltd | Information & communication | 2010 |
| Agility Insight Limited | Information & communication | 2014 |
| Agincourt UK Properties Limited | Real estate | 2023 |
| Agk-World Ltd | Manufacturing | 2015 |
| Agki Group Ltd | Wholesale & retail | 2025 |
| Agora Talent Limited | Administrative & support | 2016 |
| AGW Mechanical Ltd | Construction | 2019 |
| AHP Partners London Limited | Financial services | 2018 |
| Aidrx Strategy Consulting Ltd | Professional & scientific | 2025 |
| Aikyam Group Ltd | Information & communication | 2021 |
| AIM Educational Services Limited | Education | 2013 |
| Aima Construction Ltd | Construction | 2023 |
| Airservices UK Limited | Professional & scientific | 2000 |
| Aisha Tutors Ltd | Education | 2021 |
| AJ & Sons Property Development Ltd | Construction | 2025 |
| AJ Cabling Civils Ltd | Construction | 2023 |
| AJ Housing Ltd | Real estate | 2020 |
| AJ Winter Consulting Limited | Professional & scientific | 2025 |
| AJC Logistics Ltd | Transport & logistics | 2015 |
| Ajitk Ltd | Health & social care | 2015 |
| AJK Property Holdings Ltd | Real estate | 2023 |
| AJT Design Ltd | Professional & scientific | 2026 |
| AJT Productions Ltd | Arts & recreation | 2025 |
| Ajwashire Food Company Ltd | Wholesale & retail | 2023 |
| AK Wrap Ltd | Wholesale & retail | 2018 |
| Ak's Immigration & Consulting Services Ltd | Professional & scientific | 2025 |
| AKA Catering Consultancy Limited | Hospitality | 2018 |
| Akaem Limited | Real estate | 2025 |
| Akishan Ltd | Real estate | 2024 |
| Akita Developments Ltd | Construction | 2024 |