| A1 Environmental Services Ltd. | Construction | 1996 |
| A1 Tank Services Limited | Administrative & support | 2007 |
| A2B Taxis (Northallerton) Limited | Transport & logistics | 2003 |
| A2B Taxis Northallerton Holdings Limited | Financial services | 2018 |
| A2Z Real Estate Ltd | Construction | 2021 |
| A3 Petro Limited | Mining & quarrying | 2022 |
| AA82 Ltd | Wholesale & retail | 2022 |
| AAA Consultants Ltd | Professional & scientific | 2022 |
| Aaims Design&Build Limited | Construction | 2022 |
| Aaims GRIMSBYINVESTMENT1 Limited | Real estate | 2024 |
| Aaims Medical Consulting Limited | Professional & scientific | 2021 |
| Aansh Property Ltd | Real estate | 2021 |
| Aardvarc Electrical Engineering Ltd | Extraterritorial | 2013 |
| AAV Global Ltd | Information & communication | 2021 |
| AB Khan Traffic Ltd | Construction | 2023 |
| Abacus Carpet Company Limited | Wholesale & retail | 1986 |
| Abacus Express Logistics Limited | Transport & logistics | 2007 |
| Abba Academy Limited | Education | 2017 |
| Abberton Medical Services Ltd | Health & social care | 2011 |
| Abbeybay Properties Limited | Real estate | 2005 |
| ABC Handyman Services Limited | Construction | 2025 |
| Abel Strength and Conditioning Ltd | Education | 2024 |
| Abere Electronics Limited | Wholesale & retail | 2026 |
| Ableaim Limited | Real estate | 2000 |
| Absolute Consulting Services Ltd | Administrative & support | 2006 |
| Absolute Energy Capital LLP | | 2008 |
| Absolutely Capital Consulting Limited | Professional & scientific | 2019 |
| Absolutelyconstant Ltd | Construction | 2012 |
| Abstract Ideas Limited | Information & communication | 2004 |
| Abstract London Ltd | Manufacturing | 2020 |
| Abyl Applications Limited | Information & communication | 2015 |
| AC Aeronautical Limited | Manufacturing | 2010 |
| Acacia Springs Limited | Real estate | 2016 |
| Academic Tutor Services Ltd | Administrative & support | 2017 |
| Acara Developments Limited | Real estate | 2017 |
| Acara Management Limited | Real estate | 2012 |
| Acara Residential Limited | Real estate | 2019 |
| Accelerate Consulting International Ltd | Professional & scientific | 2023 |
| Accellor UK Limited | Information & communication | 2015 |
| Accessgrand Limited | Information & communication | 2002 |
| Accorder Music Publishing Limited | Information & communication | 2008 |
| ACCOUNTING365 Limited | Professional & scientific | 1995 |
| Ace Aesthetics Skin Clinic Limited | Other services | 2018 |
| Acelo Limited | Professional & scientific | 2023 |
| Achieveon Ltd | Professional & scientific | 2019 |
| Achievr Limited | Information & communication | 2015 |
| Acklam Hall Estates Limited | Real estate | 2015 |
| ACM Bricklehurst Limited | Real estate | 2023 |
| ACM Burgess Limited | Real estate | 2023 |
| Acme Flooring Ltd | Information & communication | 2011 |
| Acomb Construction Holdings Limited | Financial services | 2017 |
| Acomb Construction Limited | Construction | 1991 |
| Acorn Design & Develop Limited | Construction | 2016 |
| ACP 8018 Ltd | Real estate | 2021 |
| Acsian Limited | Professional & scientific | 2024 |
| Action Medics Limited | Health & social care | 2019 |
| Activationcode Ltd | Professional & scientific | 2019 |
| Active Gaming Ltd | Information & communication | 2022 |
| Active Travel Group Bidco Limited | Professional & scientific | 2016 |
| Active Travel Group Limited | Financial services | 2016 |
| Active Travel Group Midco Limited | Professional & scientific | 2016 |
| Actuarial Risk Management International Limited | Financial services | 2024 |
| Actv Two Ltd | Arts & recreation | 2024 |
| Acumentive Limited | Information & communication | 2005 |
| AD Astra Polo Ltd | Arts & recreation | 2025 |
| AD Capital Markets Ltd | Administrative & support | 2020 |
| AD Developers Ltd | Construction | 2023 |
| Adalar Ltd | Information & communication | 2017 |
| Adam Brennan Consulting Ltd | Wholesale & retail | 2025 |
| Adams Tax and Accountancy Services Limited | Professional & scientific | 2010 |
| Adaptation Architecture Limited | Professional & scientific | 2014 |
| Addict Angels Limited | Arts & recreation | 2013 |
| Addmustard Ltd. | Information & communication | 2012 |
| Addo Limited | Professional & scientific | 2017 |
| Adesso Deli Limited | Hospitality | 2017 |
| Adhc Group Limited | Real estate | 2026 |
| ADI Facades Ltd | Construction | 2015 |
| ADI Properties Ltd | Real estate | 2025 |
| Aditya IT Consultants Limited | Information & communication | 2007 |
| Adrenalin (North Yorkshire) Limited | Arts & recreation | 2002 |
| Adrenalin Shock Limited | Arts & recreation | 2016 |
| Adryas Ltd | Professional & scientific | 2015 |
| Advanced Energy Minerals (UK) Limited | Manufacturing | 2020 |
| Advanced Engineering & Surveying Limited | Construction | 2014 |
| Advanced Systems House Limited | Extraterritorial | 2009 |
| Adventure Attractions Limited | Arts & recreation | 1992 |
| Advise Legal Consultancy Ltd | Professional & scientific | 2017 |
| Aedas UK Limited | Professional & scientific | 2023 |
| Aegis Corporate Strategy Limited | Financial services | 1989 |
| Aeon Prime Ltd | Real estate | 2025 |
| Aerial Exposure Group Limited | Financial services | 2025 |
| Aerial Exposure Ltd | Manufacturing | 2016 |
| Aerial Speed Icons Limited | Wholesale & retail | 2019 |
| Aerium Flight Training Limited | Transport & logistics | 2024 |
| Aethos Design and Build Limited | Construction | 2024 |
| Aethos Project Management Limited | Construction | 2024 |
| Aevos Performance Ltd | Manufacturing | 2025 |
| AF ABL Ltd | Administrative & support | 2020 |
| Affinity International Ltd | Wholesale & retail | 2015 |
| Africa Sky Limited | Professional & scientific | 2006 |