| Accountancy Tutor (UK) Limited | Professional & scientific | 1983 |
| Accountancy-Trainingcompany.Co.Uk Limited | Education | 2015 |
| Accountics LLP | | 2017 |
| Accounting & Analysis Services Ltd | Information & communication | 2009 |
| Accounting & Tax Services Ltd | Professional & scientific | 1997 |
| Accounting and Financial Advisory Ltd | Information & communication | 2012 |
| Accrue Marlin Limited Partnership | | 2014 |
| Acctiva Limited | Information & communication | 2001 |
| Accureg Ltd | Professional & scientific | 2011 |
| Ace Car LDN Limited | Wholesale & retail | 2026 |
| Ace Cold Ltd | Manufacturing | 2023 |
| Ace Fuels Limited | Wholesale & retail | 2013 |
| Ace Housing London Ltd | Real estate | 2025 |
| Ace Long Investments Limited | Real estate | 2021 |
| Ace Medvalue Communications Ltd | Professional & scientific | 2024 |
| Ace of Tech Ltd | Information & communication | 2018 |
| ACI Group Ltd | Wholesale & retail | 2018 |
| ACM Distribution Limited | Construction | 2017 |
| Acorn Residential Management Services Limited | Real estate | 1999 |
| Acorn SA Ltd | Real estate | 2019 |
| Acorn to Oak Holdings Ltd | Financial services | 2025 |
| ACS Couriers Ltd | Transport & logistics | 2006 |
| Action Sustainability Community Interest Company | Administrative & support | 2006 |
| Active Building Services Limited | Extraterritorial | 2009 |
| Active Data Cabling Limited | Extraterritorial | 2009 |
| Active Electrical Limited | Extraterritorial | 2007 |
| Active Electrical Services Limited | Construction | 2002 |
| Active Electricians Limited | Extraterritorial | 2007 |
| Active Global Ltd | Education | 2024 |
| Active Health Clinics Limited | Health & social care | 2009 |
| Active Heating and Plumbing Services Limited | Extraterritorial | 2007 |
| Active Keyholding Limited | Extraterritorial | 2009 |
| Active Locksmiths Limited | Extraterritorial | 2006 |
| Active Plumbers Limited | Extraterritorial | 2007 |
| Active Property Maintenance Limited | Extraterritorial | 2009 |
| Active Security & Fire Limited | Extraterritorial | 2007 |
| Active Security and Locksmiths Limited | Extraterritorial | 2006 |
| Active Security Ltd | Extraterritorial | 2005 |
| Active Software Platform UK Ltd | Information & communication | 2023 |
| Actus Industries Limited | Administrative & support | 2008 |
| ACU Herbs Health Limited | Health & social care | 2021 |
| ACU Land Limited | Health & social care | 2022 |
| AD Digital Ltd | Information & communication | 2026 |
| AD LIB Pubs Ltd | Hospitality | 2020 |
| ADA Collective Ltd | Information & communication | 2025 |
| Adalchemy Holdings Ltd | Financial services | 2025 |
| Adam Cars & Travel Ltd | Transport & logistics | 2019 |
| Adamson Construction Group Ltd | Construction | 1989 |
| ADB Consult Limited | Professional & scientific | 2011 |
| ADD Couriers Ltd | Transport & logistics | 2018 |
| ADD HR Ltd | Administrative & support | 2011 |
| Added Value Financial Consulting Services Limited | Professional & scientific | 2008 |
| Addiem VA Limited | Administrative & support | 2023 |
| Addition Communications Ltd | Information & communication | 2013 |
| Addition International Limited | Administrative & support | 2006 |
| Addy Traders Ltd | Manufacturing | 2025 |
| Adelphi Assets Limited | Real estate | 2000 |
| Adelstow Advisory Limited | Professional & scientific | 2024 |
| Adept IT Ltd | Information & communication | 2020 |
| Adept-Tec Limited | Information & communication | 2012 |
| Adige World UK Limited | Wholesale & retail | 2022 |
| Adipop Limited | Professional & scientific | 2026 |
| Adirobert Interiors Ltd | Construction | 2019 |
| Admicity Ltd | Information & communication | 2023 |
| ADN Creation Limited | Wholesale & retail | 2022 |
| Adrena Technologies Ltd | Information & communication | 2023 |
| Adroit Physio Ltd | Other services | 2023 |
| Adult Adhd Clinic Ltd | Health & social care | 2022 |
| Advance Crystal Security Ltd | Professional & scientific | 2021 |
| Advanced Facial Surgery Limited | Health & social care | 2013 |
| Advanced Industrial Repair Group Ltd | Manufacturing | 2025 |
| Advanced IP Solutions Limited | Information & communication | 2016 |
| Advanced Marine Group Ltd | Financial services | 2020 |
| Advanced Marine Tenders Ltd | Professional & scientific | 2019 |
| Advanced Plastics (South Wales) Limited | Hospitality | 1997 |
| Adventure Television Limited | Information & communication | 2008 |
| Advercado Media Ltd | Wholesale & retail | 2022 |
| Advertising Waste Management Ltd | Professional & scientific | 2024 |
| Advisetheadvice Ltd | Education | 2020 |
| Adya Group Ltd | Financial services | 2020 |
| AEM Holdings Group Ltd | Hospitality | 2026 |
| Aeoncorp Asset Holding Ltd | Professional & scientific | 2024 |
| Aequitas Bidco Limited | Financial services | 2024 |
| Aequitas Topco Limited | Financial services | 2024 |
| Aeropix Limited | Other services | 2014 |
| Aeroptimo Ltd | Professional & scientific | 2019 |
| Aerospace Fasteners Ltd | Administrative & support | 1984 |
| Aesthetic Consulting Limited | Professional & scientific | 2025 |
| Aesthetic Equity Partners Limited | Financial services | 2025 |
| Aesthetic Holdings Limited | Financial services | 2019 |
| Aesthetic Resolution ADR Limited | Professional & scientific | 2025 |
| Aesthetic Resolution Holdings Limited | Financial services | 2025 |
| Aesthetic Resolution IP Limited | Information & communication | 2025 |
| Aesthetic Resolution Services Limited | Information & communication | 2025 |
| Aesthetic Shift Ltd | Construction | 2023 |
| Aesthetics by Shanty Limited | Other services | 2025 |
| Aevum Limited | Information & communication | 2026 |
| Affinity Merchandise Limited | Professional & scientific | 2014 |
| Affleck Energy Limited | Professional & scientific | 2018 |
| Affordable PCO Hire Ltd | Transport & logistics | 2023 |