| Apex Global Limited | Sevenoaks | 2001 |
| Apex Gold & Diamond Ltd | London | 2020 |
| APJ OIL & GAS Ltd | Petworth | 2018 |
| APJ OIL & GAS Resources Ltd | Petworth | 2011 |
| APK Contractors Limited | Camberley | 2021 |
| App International Export&Import Co., Ltd | Stafford, | 2024 |
| Appelbridge Limited | Farnham | 2017 |
| Appleton Prime Corporation Ltd | London | 2022 |
| April GL Limited | St Albans | 2025 |
| Aquageo Solutions Limited | London | 2025 |
| Aqualate Aggregates Limited | Birmingham | 2015 |
| Aquasonic Ltd. | Aboyne | 2001 |
| Aquatech Engineering Services Limited | Swadlincote | 2008 |
| Aquatherm Ltd | London | 2021 |
| Aquatrek Ltd | Sheerness | 2024 |
| Aquila Royalties Limited | London | 2022 |
| AR Offshore Services Limited | Great Yarmouth | 2018 |
| AR Remediations Limited | Gloucester | 2022 |
| AR5 PLC | London | 2009 |
| Arabian Nubian Mining Limited | Glastonbury | 2021 |
| Arabian Nubian Resources Ltd | Glastonbury | 2020 |
| Aram Resources Limited | Birmingham | 1997 |
| ARB Engineering Ltd. | Aberdeen | 2006 |
| Arbeth Management Ltd. | Dunblane | 2011 |
| Arbutus Renewables Limited | London | 2003 |
| ARC Quarries Ltd | Belfast | 2018 |
| ARC Technical Services Ltd | London | 1990 |
| Arcane Subsea Limited | Aberdeen | 2022 |
| Arcelormittal Mining UK Limited | London | 2002 |
| Archean Mining Consultants UK Ltd | Belfast | 2025 |
| Archer (UK) Limited | Aberdeen | 2002 |
| Archer Consulting Resources Limited | Aberdeen | 2004 |
| Archer Well Company International Limited | Eastleigh | 2015 |
| Archer Well Services (Saudi Arabia) Limited | Aberdeen | 2019 |
| Archibald Nott and Sons Limited | Tiverton | 1972 |
| Archibald Subsea Services Limited | Aberdeen | 2018 |
| Architectural Outfitting Solutions Ltd | Edinburgh | 2024 |
| Arcius Energy Egypt Limited | Middlesex | 2024 |
| Arcius Energy Limited | Sunbury On Thames | 2024 |
| Arctic Basin Ltd | Chorley | 2023 |
| Arcturus (Kirton) Limited | Brigg | 2024 |
| Arcus Limited | Aberdeen | 2000 |
| ARD Builders Ltd | Sunderland | 2026 |
| Arden Aggregates Limited | Leamington Spa | 2021 |
| Arden Midlands Limited | Coventry | 2011 |
| Ardlogie Drilling Ltd | Turriff | 2010 |
| Ardmore Resources Limited | Guildford | 1997 |
| Ardstraw Quarries Ltd | Strabane | 2011 |
| Areani Resources Limited | Dover | 2021 |
| Arenite Petroleum Limited | 4/5 Golden Square | 2014 |
| Arete Energy Limited | Bracknell | 2025 |
| Argala Limited | London | 2015 |
| Argus Black Swan Limited | Rushden | 2013 |
| Argus Fertilizer Industry Co., Ltd | Kington | 2022 |
| Argus Vector Well Systems Ltd | Aberdeen | 2026 |
| Argyll Metals Limited | Kingston Upon Thames | 2022 |
| Ariana Resources PLC | London | 2005 |
| Ariva Consultancy Limited | Bedford | 2017 |
| Arizac Rope Access Ltd | Blackpool | 2018 |
| ARK Resources Limited | Beaconsfield | 2016 |
| Arkane Technology Ltd | Linlithgow | 2019 |
| Arkansas Gold Mining Corp Limited | Renfrew | 2014 |
| Arken Engineering Ltd | Kilmarnock | 2016 |
| Armagh Gold Limited | Co Down | 2001 |
| Armetor Ltd | Edinburgh | 2016 |
| Armfield Offshore PCS Limited | Norwich | 2014 |
| Armour Group Limited | London | 2021 |
| Armstrong Safety Limited | Aberdeen | 2011 |
| Armstrongs Aggregates Limited | Bolton | 1986 |
| Arnl Limited | Stanmore | 2011 |
| Arnol Offshore Limited | Isle Of Lewis | 2024 |
| Arnolium PLC | London | 2025 |
| ARP Testing Services Ltd | Norwich | 2014 |
| ARQ Services Ltd | Aberdeen | 2023 |
| Arqam Ltd | London | 2020 |
| Arran Aggregates Ltd. | Isle Of Arran | 1999 |
| Array Training Limited | Aberdeen | 2012 |
| Arrow Subsea Limited | Peterhead | 2016 |
| ARS Investment Holding Ltd | London | 2022 |
| Arthur Mining Support Services Ltd | Goole | 2021 |
| Arvo Lithium Ltd | Cranbrook | 2022 |
| AS BID Co Limited | London | 2025 |
| AS S Realisations Limited | Leeds | 2009 |
| ASA Headco Limited | Accrington | 2017 |
| ASA Resource Group Limited | Accrington | 1987 |
| Asanco Limited | Aberdeen | 2010 |
| Asbasra Ltd | Wolverhampton | 2023 |
| Asbold Limited | London | 2025 |
| Ascendancy Advisors Ltd | London | 2023 |
| Ascension Earth Resources Ltd | Oxford | 2024 |
| Ascent D1 Ltd | London | 2024 |
| Ascent Resources PLC | London | 2004 |
| ASF Services Limited | Dunblane | 2019 |
| ASH Access Ltd | Hull | 2025 |
| Ashburn Brothers Limited | Preston | 1985 |
| Ashclinton Ltd | Luton | 2019 |
| Ashcourt (Cumbria) Limited | York | 2003 |
| Ashcourt (Northumberland) Limited | York | 1975 |
| Ashcourt Quarries Limited | Pocklington | 2019 |
| Ashebrook Ltd | Warrington | 1997 |