| A-Squared Consulting Limited | London | 2012 |
| A-Star Educational Publishing Limited | Lancashire | 2003 |
| A-Systems Safety Ltd | Worcester | 2015 |
| A-Team Fintech Consultants Limited | Glasgow | 2022 |
| A-Team Rigging Ltd | Felixstowe | 2014 |
| A-Tech Associates Ltd | Dagenham | 2018 |
| A-Tech IT Services Limited | Salford | 2013 |
| A-Tech Repair Centre Ltd | Salford | 2015 |
| A-Tech Services Limited | Poole | 2003 |
| A-Tech Solutions (UK) Ltd | Birmingham | 2022 |
| A-Tech Studio Services Ltd | Whitstable | 2024 |
| A-Tek Solutions Limited | London | 1999 |
| A-Tel Solutions Limited | Southampton | 2012 |
| A-Telecom Limited | London | 2019 |
| A-Touch Ltd | London | 2007 |
| A-Ward Web Services Ltd | Norwich | 2025 |
| A-Wd Web Design Ltd | Milton Keynes | 2024 |
| A-Z Communications and Consultants Ltd | London | 2013 |
| A-Z & Sons Ltd. | | 2001 |
| A-Z Analysis Ltd | London | 2026 |
| A-Z Business Limited | Sudbury | 2002 |
| A-Z Communication Services Limited | Birmingham | 2006 |
| A-Z Comprehensive Solutions Ltd | London | 2023 |
| A-Z Consulting Ltd | Knowle | 2024 |
| A-Z Digital Solutions Ltd | Stockport | 2017 |
| A-Z Dynamics Group Ltd | London | 2023 |
| A-Z Films Limited | London | 2006 |
| A-Z Fusion Ltd | London | 2024 |
| A-Z Group Limited | Redhill | 1996 |
| A-Z Horizon Innovations Ltd | London | 2024 |
| A-Z IT Security Limited | Stoke-On-Trent | 2013 |
| A-Z Nexus Ltd | London | 2023 |
| A-Z SAP Logistics Support Limited | Harrow | 2019 |
| A-Z Software Sales Ltd | Royston | 2016 |
| A-Z Softwares Limited | Birmingham | 2020 |
| A-Z Solution London Ltd | London | 2026 |
| A-Z Tech Ventures Ltd | London | 2024 |
| A-Z Ultimate Guide Ltd | Stoke-On-Trent | 2023 |
| A-Z Zenith Technologies Ltd | London | 2023 |
| A-Zcomputing Limited | High Wycombe | 2015 |
| A-Zelkova Limited | Northampton | 2004 |
| A. & C. Black (Distribution) Limited | London | 1974 |
| A. & C. Black Limited | London | 1915 |
| A. a. Woodward Publishing Limited | Winsford | 2025 |
| A. Allsopp Marketing Ltd | Wallsend | 2022 |
| A. Amor Writes Limited | London | 2020 |
| A. Arfa Ltd | London | 2025 |
| A. B. Cadwork Ltd | Manchester | 2007 |
| A. Chauhan Consulting Ltd | Leicester | 2012 |
| A. Corp Ltd | Southsea | 2018 |
| A. Devlin Services Limited | Manchester | 2004 |
| A. F. Green Factors Limited | Berkhamsted | 2000 |
| A. G. E Productions Ltd | London | 2021 |
| A. Garratt Services Limited | Bedford | 2011 |
| A. Gillespie Associates Limited | Glasgow | 2001 |
| A. H. Cameras Ltd | Liverpool | 2022 |
| A. H. DE Quatre Ltd. | London | 2014 |
| A. Hayward & SON Limited | Newcastle Emlyn | 1991 |
| A. I. Gelber Ltd | Market Harborough | 2025 |
| A. J. Seeley Limited | Welwyn Garden City | 2006 |
| A. L. French Ltd | Warrington | 2021 |
| A. Leete Consultancy Limited | Dorchester | 2023 |
| A. Mika Limited | Peterborough | 2017 |
| A. R. L. Software Limited | Sanquhar | 2006 |
| A. Tsifouti LAB Ltd | London | 2026 |
| A. Williamson Ltd | Worthing | 2023 |
| A. Zadkiel Ltd | West Kirby | 2007 |
| A. Zen.Productions Videography Limited | Surbiton | 2019 |
| A.A Digital Solutions Ltd | London | 2024 |
| A.A Edits Ltd | Sowerby Bridge | 2023 |
| A.A. Effects Ltd | Watford | 2016 |
| A.A. Enterprise Consulting Ltd | London | 2026 |
| A.A.C. Services Limited | | 1989 |
| A.A.E Consult Ltd | Russett Way | 2021 |
| A.Allan Limited | Epsom | 2009 |
| A.Andaloussi Art Studio Ltd | London | 2023 |
| A.Anderton Consultancy Ltd | Warwick | 2016 |
| A.B. Ascend Ltd | Isleworth | 2024 |
| A.B. Studios Limited | Bromborough | 1990 |
| A.B.J. Comms Ltd | Birmingham | 2012 |
| A.B.M. Solutions Ltd | Dorchester | 1998 |
| A.Barik Ltd. | London | 2018 |
| A.C Economic Research Limited | London | 2023 |
| A.C Hillz Ltd | London | 2025 |
| A.C. Fibres Limited | Liverpool | 2015 |
| A.C. Independence Limited | Hereford | 1997 |
| A.C. Productions Limited | Borehamwood | 2007 |
| A.C.J. Computer Services Limited | London | 1988 |
| A.C.N Data & Cctv Installations Ltd | Fareham | 2024 |
| A.Central Ltd | Wigan | 2016 |
| A.Ceylan Ltd | London | 2018 |
| A.CO11ECTIVE Ltd | Minehead | 2025 |
| A.Cohen & Co.,(Great Britain)Limited | Tunbridge Wells | 1970 |
| A.D Jeriel Ltd | London | 2015 |
| A.D. Artworks Ltd | London | 2024 |
| A.D. Stewart I.G. Consultancy Limited | Motherwell | 2018 |
| A.D.C. Systems Limited | Staffordshire | 1992 |
| A.D.D. Special Effects Limited | Tadworth | 1999 |
| A.D.E Solutions Limited | Orpington | 2011 |
| A.D.J Film Limited | Reading | 2016 |