| ADS Plant Services Ltd | Manufacturing | 2015 |
| Adults Aligned Ltd | Education | 2024 |
| Advance Car and Commercial Services Ltd | Wholesale & retail | 2020 |
| Advanced Building Concept Ltd | Construction | 2013 |
| Advanced Property Management Limited | Real estate | 2014 |
| Advanced Windows (Stockton) Limited | Construction | 2019 |
| Adventure Access CIC | Wholesale & retail | 2019 |
| Adventuron Software Limited | Information & communication | 2019 |
| Aecs Engineering Ltd | Professional & scientific | 2025 |
| AEE Offshore Services Ltd | Manufacturing | 2026 |
| AES Digital Solutions Limited | Information & communication | 1992 |
| Aesthetics by AMO Training Academy Ltd | Education | 2025 |
| Aesthetics Shop UK Ltd | Wholesale & retail | 2024 |
| AET Safety UK Limited | Professional & scientific | 2018 |
| AF Inspection & NDT Ltd | Professional & scientific | 2024 |
| AF Property Services Ltd | Real estate | 2025 |
| Affotek Limited | Manufacturing | 2014 |
| Affx Marketing Ltd | Professional & scientific | 2022 |
| Afmx Ltd | Wholesale & retail | 2024 |
| African Harvest Limited | Wholesale & retail | 2025 |
| Africayamuka Limited | Financial services | 2025 |
| AG Physiotherapy Ltd | Health & social care | 2026 |
| AG47 Energy Ltd | Construction | 2018 |
| Agbonsoft Ltd | Wholesale & retail | 2024 |
| Ageing Better Ltd | Administrative & support | 2016 |
| AGM Property Lettings Limited | Real estate | 2024 |
| Agri Spark Limited | Construction | 2017 |
| Agri Water Wells Limited | Agriculture & fishing | 2025 |
| Agricultural Forestry & Plant Limited | Administrative & support | 2022 |
| AGS Bowes Pipefitting Limited | Construction | 2024 |
| Agtraining-Cpc Ltd | Education | 2021 |
| Agua Bathrooms & Kitchens Limited | Other services | 2020 |
| AH Offshore Services Ltd | Construction | 2025 |
| AHG Partners Ltd | Professional & scientific | 2026 |
| AHH NE Ltd | Hospitality | 2022 |
| Ahhfp Limited | Agriculture & fishing | 2023 |
| AHJ Joinery Limited | Construction | 2016 |
| Ahmed Foods NE Ltd | Wholesale & retail | 2025 |
| AI Mobility Group Ltd | Financial services | 2025 |
| AI Mobility Holdings Ltd | Real estate | 2025 |
| Aidigitalz Ltd | Professional & scientific | 2025 |
| Aigteesside Ltd | Construction | 2025 |
| Aiia Consultancy and Management Limited | Professional & scientific | 2021 |
| AIM North Trading Ltd | Wholesale & retail | 2026 |
| AIM Properties (NE) Limited | Real estate | 2017 |
| Aimdyl Ltd | Administrative & support | 2017 |
| Aimee Willmott Limited | Arts & recreation | 2014 |
| Airbourne Aviation Services Ltd | Manufacturing | 2024 |
| Aircon Group Holdings Ltd | Financial services | 2023 |
| Aircon Group Limited | Extraterritorial | 2018 |
| Aircon-Refrigeration Limited | Construction | 1963 |
| Airthrey Consulting Ltd | Information & communication | 2021 |
| AIT Mitra Limited | Health & social care | 2015 |
| AJ Diagnostics Ltd | Health & social care | 2025 |
| AJ Electrical Ltd | Construction | 2018 |
| AJ Jack Logistics Ltd | Transport & logistics | 2025 |
| AJA Mechanical Services Limited | Administrative & support | 2015 |
| AJC Decor Ltd | Construction | 2024 |
| AJC Electrical Contractors Limited | Construction | 2022 |
| AJC Electrics Limited | Construction | 2017 |
| AJE Drone Services Ltd | Professional & scientific | 2020 |
| AJF Blade Repair Services Limited | Professional & scientific | 2026 |
| AJH Energy Limited | Energy | 2014 |
| AJH Offshore Ltd | Administrative & support | 2012 |
| AJH Synth Limited | Manufacturing | 2021 |
| AJJ Autos Ltd | Wholesale & retail | 2015 |
| AJK Accounting Services Ltd | Professional & scientific | 2019 |
| AJK Enterprises Ltd | Transport & logistics | 2024 |
| AJN Property Partners Ltd | Real estate | 2026 |
| Ajokeblings Ltd | Wholesale & retail | 2025 |
| AJT Cable Jointing Limited | Manufacturing | 2023 |
| AJW Business Consultancy Services Limited | Professional & scientific | 2026 |
| AK Banerjee Ltd | Health & social care | 2024 |
| AK North East Limited | Administrative & support | 2014 |
| AK Properties NE Ltd | Real estate | 2022 |
| AKA Connect Limited | Wholesale & retail | 2025 |
| AKA Midlands Distribution Ltd | Wholesale & retail | 2026 |
| AKF Engineering Ltd | Construction | 2026 |
| AKH Locums Ltd | Professional & scientific | 2015 |
| Akhomes Ltd | Real estate | 2015 |
| AKL Leisure Limited | Hospitality | 2019 |
| AKO Pizzeria Ltd | Hospitality | 2026 |
| Akour Services Limited | Administrative & support | 2025 |
| AKT Traders Limited | Wholesale & retail | 2025 |
| AL Carpets & Flooring Ltd | Wholesale & retail | 2026 |
| AL Holborn Limited | Administrative & support | 2018 |
| Al-Hussain Enterprise Ltd | Transport & logistics | 2019 |
| Alacer Ltd | Information & communication | 2017 |
| Alan Hollingsworth Financial Solutions Ltd | Financial services | 2020 |
| Alan P Brown & Co Limited | Professional & scientific | 2014 |
| Albert Court Property Limited | Real estate | 2021 |
| Albrough Homes Limited | Construction | 2015 |
| Aldwark Arms PUB Ltd | Hospitality | 2020 |
| Aleena and Aliyah Limited | Construction | 2024 |
| Alewood Group Ltd | Information & communication | 2025 |
| Alex Walker Tree Care Limited | Agriculture & fishing | 2019 |
| Alexanders Autos Limited | Wholesale & retail | 2025 |
| Alexandra Builders Limited | Construction | 2003 |
| Alfa Minibus Ltd | Transport & logistics | 2017 |
| Alfrando's Peri Peri Ltd | Hospitality | 2026 |