| Acgl Limited | Cheltenham | 2023 |
| ACH Composites Ltd | Tamworth | 2025 |
| ACH Grapes Limited | Canterbury | 2023 |
| ACH Technical Ltd | Bedford | 2023 |
| Achar Bari Limited | London | 2025 |
| Achavinish Ltd | Isle Of Gigha | 2022 |
| Achech UK Ltd | Birmingham | 2016 |
| Aches Ltd | Wisbech | 2023 |
| Acheson & Acheson Limited | Altrincham | 1992 |
| Acheulean Design Ltd | Blackburn | 2024 |
| Achicha Ltd | London | 2025 |
| Achievement TV Ltd | Huddersfield | 2013 |
| Achiles Aviation Maintenance Ltd | Cambridge | 2024 |
| Achilleas Limited | Rochester | 2007 |
| Achilles Therapeutics PLC | Birmingham | 2020 |
| Achilleus Medical UK Ltd | Hayes | 2022 |
| Achiltibuie Highland Reeds Ltd. | West Lothian | 2003 |
| Achimille Ltd | Banchory | 2013 |
| Achnacarry Limited | Stewarton | 2015 |
| Achnacreemore Limited | North Connel | 2015 |
| Achtis Ltd. | Grimsby | 2013 |
| ACI Construction Ltd | Middlesbrough | 2026 |
| ACI Contracting Ltd | Chepstow | 2022 |
| ACI Home Improvement Limited | Hove | 2024 |
| ACI Industrial Holding Ltd | Beckenham | 2012 |
| Acibo Ltd | Basildon | 2025 |
| Acien Limited | London | 2024 |
| Acier Fabrications Ltd | Hyde | 2021 |
| Acier Manufacturing Limited | London | 2025 |
| Acies Medical Techology Limited | Milton Keynes | 2025 |
| Aciex Ltd | Brierley Hill | 2026 |
| Acil Limited | Malvern | 2019 |
| Acing UK Limited | London | 2011 |
| Aciobanitei Cristian Ltd | Cambridge | 2025 |
| Acium Ltd | Stevenage | 2015 |
| Aciva Limited | London | 2020 |
| Acix Systems Limited | Nottingham | 2025 |
| ACJ Aluminium Manufacturing & Maintenance Ltd | Cannock | 2023 |
| ACJ Educational Services Limited | Beaconsfield | 2011 |
| ACJ Furniture Ltd | Bromsgrove | 2020 |
| ACJ Joiners Ltd | Musselburgh | 2024 |
| ACK Engineering Ltd | Chelmsford | 2013 |
| ACK Enterprises Ltd | Milton Keynes | 2006 |
| ACK Manufacturing Ltd | Bristol | 2020 |
| Ackerman Engineering Limited | Bridport | 1976 |
| Ackery Brands Limited | Macclesfield | 2012 |
| Ackery London Limited | Much Wenlock | 2018 |
| Acketts Services Limited | Chelmsford | 2016 |
| Acklam Black Ltd | London | 2019 |
| Acklam Maintenance Services Limited | Middlesbrough | 1997 |
| Ackland Lifts Limited | Bristol | 2024 |
| Acksen Ltd | Newtownabbey | 1986 |
| ACL (2002) Limited | West Bromwich | 2002 |
| ACL (Structural Steel) Limited | Bishop Auckland | 2013 |
| ACL Clothing Ltd | London | 2017 |
| ACL Electrical North West Limited | Chorley | 2012 |
| ACL Exhibitions Ltd | Ryde | 2020 |
| ACL Installations Limited | Wigan | 2026 |
| ACL Ireland Ltd | Londonderry | 2022 |
| ACL Packaging Solutions Limited | Bristol | 2004 |
| ACL Refrigeration & Air Conditioning Ltd | Castleford | 2010 |
| Aclain Limited | Chessington | 2004 |
| Acle Urban Gardens Limited | Acle | 2016 |
| Aclmo Limited | Prestonpans | 2025 |
| Acloque Capital Limited | London | 2015 |
| ACM Acoustic Engineering Limited | Brentwood | 1993 |
| ACM Bearings Limited | Rotherham | 1991 |
| ACM Engineer Ltd | Cambridge | 2022 |
| ACM Instruments Ltd. | Grange-Over-Sands | 2022 |
| ACM Maintenance Limited | Lutterworth | 2009 |
| ACM Meat Factory Ltd | Barking | 2017 |
| ACM Print Management Limited | Maidstone | 2017 |
| ACM Rolling Stock Ltd | Paisley | 2025 |
| ACM Technics Limited | Birmingham | 2017 |
| ACM Tooling UK Ltd | Leeds | 2024 |
| ACM Trading Ltd. | Brighouse | 2009 |
| ACM Welding Services Limited | Corby | 2015 |
| ACM Woodworking Machines Ltd | Gillingham | 2014 |
| Acme Air Power Limited | Ardrossan | 2025 |
| Acme Aviation Limited | Norwich | 2013 |
| Acme Coffee Ltd | Newcastle | 2024 |
| Acme Compactors Ltd | Sheffield | 2024 |
| Acme Creative Ltd | London | 2026 |
| Acme Design & Print Ltd | Portsmouth | 2007 |
| Acme Energy (IRL Holdings) Ltd | London | 2010 |
| Acme Engineering Ltd | Southall | 2021 |
| Acme Engineering Products UK Limited | Sutton Coldfield | 2016 |
| Acme Graphics Limited | Teddington | 2003 |
| Acme Metal Spinning & Bedale Limited | West Midlands | 2005 |
| Acme Refractories Limited | Stoke On Trent | 2002 |
| Acme Seals Limited | Witham | 1928 |
| Acme Securex Limited | Ilford | 2025 |
| Acme Spinning Co.(Oldbury)Limited | West Midlands | 1954 |
| Acme Stainless Limited | 34A Southgate, Sleaford | 2002 |
| Acme UK Inc Limited | Chertsey | 2018 |
| ACME2025 Limited | London | 2025 |
| Acmos U.K. Ltd. | Chester | 1986 |
| ACN - ALL the Care YOU Need Ltd | London | 2018 |
| ACN Media Ltd | Glasgow | 2014 |
| ACN NDT Services Ltd | South Ockendon | 2016 |