| ARJ Realty Ltd | Real estate | 2022 |
| ARK Business Consulting Ltd | Professional & scientific | 2024 |
| ARK Solutions Group Limited | Professional & scientific | 2018 |
| Arkitopos Ltd | Professional & scientific | 2016 |
| Arlingtontx Investment Management Limited | Real estate | 2024 |
| Arlo Hudson Limited | Wholesale & retail | 2018 |
| Armon-Jones Partners Limited | Professional & scientific | 2018 |
| Armour Home Electronics Limited | Manufacturing | 1980 |
| ARO Enterprises Limited | Real estate | 2020 |
| ARO Holdings Limited | Financial services | 2020 |
| ARO Property Development Limited | Real estate | 2020 |
| Arolla Travel Services Ltd | Administrative & support | 2020 |
| Around to IT Ltd | Construction | 2023 |
| Art AIM Limited | Professional & scientific | 1992 |
| Art Gallery 13 Limited | Arts & recreation | 2016 |
| Artek Electrical Ltd | Construction | 2022 |
| Artificial Reasoning Computer Network GPT Limited | Professional & scientific | 2021 |
| Artistic Talent Agency Ltd | Administrative & support | 2024 |
| Artmar Construction Ltd | Construction | 2020 |
| Artris Limited | Other services | 2025 |
| Artvlada Ltd | Construction | 2024 |
| AS Fire Ltd | Public administration | 2025 |
| Asan Logistics Ltd | Transport & logistics | 2014 |
| ASB Heating and Plumbing Ltd | Construction | 2019 |
| Ascalon Food Company Ltd | Wholesale & retail | 2017 |
| Ascott Blake Limited | Professional & scientific | 2016 |
| Ascott Blake Recruitment Limited | Professional & scientific | 2017 |
| Ashdene Automotive Solutions Ltd | Wholesale & retail | 2026 |
| Ashdene Property Solutions Ltd | Real estate | 2025 |
| Ashdene Technology Solutions Ltd | Information & communication | 2024 |
| Ashefelde Consulting Limited | Public administration | 2024 |
| Ashley Burns Limited | Administrative & support | 2008 |
| Ashton Webb Recruitment Limited | Administrative & support | 2014 |
| Asmin Ltd | Other services | 2016 |
| Aspock UK Limited | Wholesale & retail | 2001 |
| Assured AV Security Ltd | Administrative & support | 2024 |
| Assured Customer Experience Ltd | Professional & scientific | 2006 |
| Astaria SEC Ltd | Wholesale & retail | 2018 |
| ATA Living Ltd | Real estate | 2026 |
| Atacus Limited | Information & communication | 2014 |
| Atarus Group Ltd | Administrative & support | 2025 |
| Atbk Properties Limited | Construction | 2022 |
| Atm-Dev Limited | Information & communication | 2016 |
| Atmospheres Ventilation Services Limited | Construction | 2015 |
| Atronica Media Ltd | Wholesale & retail | 2014 |
| Atypical Works Ltd | Arts & recreation | 2020 |
| Auctor Ltd | Professional & scientific | 2012 |
| Audax Associates Ltd | Administrative & support | 2024 |
| Audiotours Ltd | Information & communication | 2025 |
| Auge Consulting Limited | Professional & scientific | 2022 |
| Augeyboyz Ltd | Information & communication | 2021 |
| Augment Corporate Finance Limited | Financial services | 2022 |
| Aunty Roxene's Beauty Products Limited | Wholesale & retail | 2024 |
| Aurora Nadine Limited | Professional & scientific | 2014 |
| Autos Site Ltd | Wholesale & retail | 2022 |
| Autotech Bishops Stortford Ltd | Wholesale & retail | 2021 |
| Auxilium (Southern) Ltd | Professional & scientific | 2021 |
| AV Build Limited | Construction | 2023 |
| AV Design Arch Ltd | Construction | 2015 |
| AV Pipework Ltd | Professional & scientific | 2025 |
| AVA Ssas Limited | Administrative & support | 2017 |
| Avalon Surveyors Ltd | Professional & scientific | 2000 |
| Avance International Supplies Limited | Wholesale & retail | 2016 |
| Avataraero Ltd | Administrative & support | 2016 |
| AVENT4U Ltd | Administrative & support | 2013 |
| Averil Sinnott Ltd | Arts & recreation | 2012 |
| AVM Workwear and Embroidery Ltd | Manufacturing | 2015 |
| Avondale Fitzrovia Ltd | Real estate | 2022 |
| Avondale Investment Holdings Ltd | Real estate | 2022 |
| Axiom Devices Ltd | Health & social care | 2023 |
| Axvera Ltd | Information & communication | 2026 |
| Ayinde Consulting Services Ltd | Professional & scientific | 2025 |
| Aynul Hoque Limited | Transport & logistics | 2025 |
| Azaan Properties Ltd | Real estate | 2020 |
| Azahar Media Ltd | Information & communication | 2021 |
| Aziza UK Consultants Limited | Professional & scientific | 2013 |
| B & C Augers Ltd | Manufacturing | 2013 |
| B&L Management Company Limited | Other services | 2017 |
| B&V Woodworkx Ltd | Construction | 2026 |
| B&V Woodworx Ltd | Construction | 2026 |
| B-Con Investments Ltd | Other services | 2023 |
| B-Con Ltd | Health & social care | 2012 |
| B-Con Naturopathy Services Ltd | Health & social care | 2023 |
| B-Con Oncology Services Ltd | Health & social care | 2023 |
| B.Y Collections Limited | Other services | 2018 |
| B2&B1 Management Ltd | Manufacturing | 2025 |
| B3 Scaffolding Limited | Construction | 2019 |
| Baby Boutique Billericay Ltd | Wholesale & retail | 2017 |
| Babyballers Bishop's Stortford Limited | Arts & recreation | 2020 |
| Babylon Garden Studio Ltd | Administrative & support | 2025 |
| Babylon Studio Limited | Information & communication | 2025 |
| Babyprints Franchising Limited | Other services | 2003 |
| Backler Francis Limited | Professional & scientific | 2019 |
| Bacqd Capital Limited | Financial services | 2025 |
| Bacqd Events Limited | Professional & scientific | 2019 |
| Bacqd FX Limited | Information & communication | 2025 |
| Bacqd Group Limited | Information & communication | 2025 |
| Bailey Bridge Ltd | Construction | 2019 |
| Baldar Construction Ltd | Construction | 2018 |
| Bali Bowls Limited | Hospitality | 2016 |