| AH ITB Limited | Hospitality | 2019 |
| AHP Electrical Limited | Construction | 2025 |
| Ahrh Property Limited | Real estate | 2024 |
| AI Abacus Ltd | Information & communication | 2020 |
| AI Investment Holdings Ltd | Real estate | 2024 |
| Airedon Limited | Professional & scientific | 2015 |
| Airey Building Limited | Construction | 2013 |
| AJB 130 Limited | Administrative & support | 2016 |
| AJC Horizon Ltd | Information & communication | 2023 |
| AJF Farriers Ltd | Agriculture & fishing | 2014 |
| AJL Audit Ltd | Public administration | 2026 |
| AJR (Keighley) Ltd | Construction | 2022 |
| AJW Business Consultancy Limited | Professional & scientific | 2022 |
| Akula Group Limited | Financial services | 2022 |
| Akula Living Limited | Manufacturing | 2016 |
| Alagos Engineering Limited | Professional & scientific | 2008 |
| Alan Townsend & Co Limited | Wholesale & retail | 1999 |
| Alens Barber Ltd | Other services | 2018 |
| Alexandra Court Bedale Limited | Households | 2005 |
| Alexandra Road Limited | Real estate | 2013 |
| Alfados Limited | Wholesale & retail | 2014 |
| Alif Taxi Ltd | Transport & logistics | 2025 |
| ALL About That Ltd | Wholesale & retail | 2023 |
| ALL Agile Limited | Information & communication | 2016 |
| ALL of US Holdings Limited | Financial services | 2020 |
| Allanfield Grove (Wetherby) Management Company Limited | Households | 2021 |
| Allegro Services Ltd | Professional & scientific | 2021 |
| Alliance Rail Ltd | Transport & logistics | 2023 |
| Allied Network Services (Leeds) Limited | Information & communication | 2004 |
| Allied Westminster (Insurance Services) Limited | Financial services | 1989 |
| Allinson Westlake Limited | Professional & scientific | 2024 |
| Allison Services Ltd | Professional & scientific | 2024 |
| Allthingsmicro Limited | Information & communication | 2015 |
| Allwood Park Ltd | Professional & scientific | 2022 |
| ALM Postcard Ltd | Hospitality | 2022 |
| Aloa C Ltd | Real estate | 2019 |
| Aloe E-Cell UK Distribution Limited | Financial services | 2025 |
| Alpaca (Front ROW) Events Ltd | Professional & scientific | 2019 |
| Alpaca Group Holdings Limited | Financial services | 2023 |
| Alpaca Investments LLP | | 2020 |
| Alpaca Opportunities Limited | Professional & scientific | 2018 |
| Alpaca Ventures Limited | Financial services | 2020 |
| ALT Group Holdings Limited | Financial services | 2016 |
| Alt-Legal Limited | Professional & scientific | 2014 |
| Alybi Ltd | Hospitality | 2018 |
| Amae Home Limited | Professional & scientific | 2025 |
| AMD Digital Ltd | Information & communication | 2023 |
| American Nails and Spa 15 Ltd | Other services | 2024 |
| AMK London Limited | Administrative & support | 2023 |
| Amor Fine Dining Limited | Hospitality | 2024 |
| Ampoulabs Ltd | Professional & scientific | 2026 |
| Anadear Estates Ltd | Real estate | 2024 |
| Ando Engineering Limited | Professional & scientific | 2018 |
| Andrew Smith Surgical Services Ltd | Health & social care | 2018 |
| Andrew's Butchers Limited | Wholesale & retail | 2007 |
| Andrews & Metcalfe Developments Limited | Construction | 2011 |
| Andrews Auto Parcs Limited | Real estate | 2000 |
| Andymc Ltd | Administrative & support | 2024 |
| Anelis Limited | Wholesale & retail | 2018 |
| Angelazia Holdings Limited | Financial services | 2023 |
| Anne Shiels Consulting Limited | Professional & scientific | 2015 |
| Ant&Teo Ltd | Hospitality | 2025 |
| Anthony Rawson Limited | Professional & scientific | 2017 |
| Anthro Search Ltd | Administrative & support | 2026 |
| Anthromachine Ltd | Professional & scientific | 2021 |
| AP1 (Group) Ltd | Construction | 2020 |
| Apex Engineering (Leeds) Ltd | Manufacturing | 2022 |
| Apex Equity Ltd | Real estate | 2026 |
| Apex Manufacturing Solutions Limited | Professional & scientific | 2023 |
| Aplomb+Brio Limited | Professional & scientific | 2019 |
| Appleson-Judd Limited | Construction | 1999 |
| Applied Laser Solutions Limited | Manufacturing | 2000 |
| Aqua Environment Solutions Ltd | Professional & scientific | 2023 |
| ARC Consultancy (Yorkshire) Limited | Professional & scientific | 2015 |
| Arcc Couriers & Storage Ltd | Transport & logistics | 2014 |
| Arch Industrial Technologies Ltd | Manufacturing | 2019 |
| Archimark Ltd | Professional & scientific | 2024 |
| Architectural Design Solutions Limited | Professional & scientific | 2000 |
| Arctic FOX Ltd | Administrative & support | 2022 |
| Ardpark Ltd | Professional & scientific | 2018 |
| Argvent Property Ltd | Real estate | 2015 |
| Arke Wellness Ltd | Arts & recreation | 2025 |
| Aroai Health Limited | Information & communication | 2019 |
| Arteon Services Limited | Wholesale & retail | 2011 |
| Arthro Dynamik Ltd | Manufacturing | 2013 |
| Arville 1000 Limited | Professional & scientific | 1919 |
| Arville Belting Limited | Manufacturing | 1938 |
| Arville Coating Limited | Manufacturing | 2024 |
| Arville Fabrication Limited | Manufacturing | 1898 |
| Arville Holdings Limited | Financial services | 2010 |
| Arville Textiles Limited | Manufacturing | 1951 |
| Arwincross Limited | Real estate | 1999 |
| ASA Technology Limited | Manufacturing | 2017 |
| Asceris Limited | Administrative & support | 2020 |
| Asclepius Healthcare Ltd | Health & social care | 2015 |
| Ashdale Projects Limited | Construction | 2010 |
| Ashdale Property Limited | Construction | 2022 |
| Ashfield Homes (Bishop Monkton) Ltd | Construction | 2023 |
| Ashfield Homes (Bishop Monkton) Rental Ltd | Construction | 2025 |
| Ashfield Homes Ltd | Construction | 2016 |