| Alta Bioscience Limited | Redditch | 2010 |
| Alta Cyclotron Services Limited | Birmingham | 2011 |
| Alta Engineering Ltd | Barnsley | 2002 |
| Alta Services Ltd | Cults | 2020 |
| Alta Vision Ltd | Hornchurch | 2022 |
| ALTA8 Limited | Ashford | 2016 |
| Altaavia Ltd | London | 2025 |
| Altaeros UK Limited | Wrexham | 2024 |
| Altaf's Kitchen Ltd | Chessington | 2021 |
| Altai Digital Ltd | London | 2018 |
| Altair (UK) Ltd | Hemel Hempstead | 2013 |
| Altair Systems Limited | Stockport | 2002 |
| Altaix Performance Ltd | Middlesbrough | 2025 |
| Altaluxa Group Ltd | London | 2022 |
| Altamash International Ltd | London | 2025 |
| Altamira Colour Limited | West Nile Street | 1993 |
| Altar of Incense Ltd | Basingstoke | 2025 |
| Altar Pottery Ltd | Liverpool | 2023 |
| Altara Containers Ltd | Chester | 2025 |
| Altaras International Worcester Limited | Ripley | 2011 |
| Altarichard Concrete Solutions Ltd | Ballymoney | 2015 |
| Altario Limited | London | 2025 |
| Altaroute Limited | Bristol | 1978 |
| Altas Standart Ltd | London | 2018 |
| Altcheese Ltd | Shepton Mallet | 2021 |
| Altec Extrusions Limited | St Austell | 1998 |
| Altec Machinery Enterprise Limited | Beckenham | 2022 |
| Altec Systems Ltd | Swansea | 2011 |
| Altech Engineering Limited | Haywards Heath | 1997 |
| Altech Fabrications Limited | West Yorkshire | 2005 |
| Altech Global Trade Limited | Oldbury | 2012 |
| Altech UK Labelling Technologies Limited | Bridgend | 2007 |
| Altechnologies Ltd | Crawley | 2019 |
| Altegra Integrated Solutions Limited | Leeds | 1993 |
| Altek Europe Limited | Chesterfield | 2007 |
| Altek International Limited | Brigg | 2008 |
| Altek Melting Solutions Limited | London | 2019 |
| Alteka Solutions Limited | Loughborough | 2020 |
| Alter EGO Brewing Co Ltd | Alfreton | 2018 |
| Alter Inc Limited | Washington | 2017 |
| Alter Installation Services Ltd | Wirral | 2025 |
| Alter Space Technologies Ltd | Maidstone | 2026 |
| Alter Technology TUV Nord UK Limited | Livingston | 2003 |
| Altera London Ltd | London | 2022 |
| Altera Technologies Limited | Telford | 2015 |
| Altera Waters Limited | Dukinfield | 2024 |
| Alteracetions Limited | Derby | 2024 |
| Alterations by Jillian Ltd | Glasgow | 2023 |
| Alterations by Michele Limited | Newton Aycliffe | 2020 |
| Alterations Suite Ltd | Pontyclun | 2024 |
| Altere Studios Limited | Bungay | 2024 |
| Altered Images Engineering Limited | Millom | 2009 |
| Alteregobeds Ltd | Hatfield | 2025 |
| Alterever Limited | Hessle | 1998 |
| Altergen Ltd | Bath | 2020 |
| Alterlith Ltd | London | 2026 |
| Alternate Electrical Services Limited | Bristol | 2014 |
| Alternate Works Limited | Batley | 2026 |
| Alternatease Limited | London | 2026 |
| Alternatech Limited | Winchester | 2015 |
| Alternative Attire Ltd | London | 2025 |
| Alternative Cars Limited | Oxford | 2003 |
| Alternative Coffee Limited | Manchester | 2019 |
| Alternative Computers Ltd | Stoke-On-Trent | 2026 |
| Alternative Design Limited | London | 2018 |
| Alternative Enterprises Limited | Trinity Way Chingford | 1992 |
| Alternative Foods London Ltd. | Farnham | 2018 |
| Alternative Glass Fibre Moulders Limited | Brecon | 2007 |
| Alternative Healing Ltd | Newtownabbey | 2020 |
| Alternative Power Solutions Limited | Hampshire | 2006 |
| Alternative Precision Sheet Metal Limited | Swansea | 1997 |
| Alternative Print Solutions Limited | Bishop'S Stortford | 2006 |
| Alternative Solutions Limited | Swindon | 1997 |
| Alternative Technology Solutions Limited | Whitehaven | 2016 |
| Alternative Trading 2020 Limited | Walsall | 2020 |
| Alternative Windows (Leeds) Limited | Cross Green Industrial Estate | 1992 |
| Alternatives to Stone Limited | Orpington | 2014 |
| Alterno Limited | Magherafelt | 2017 |
| Altertek Ltd | Southampton | 2005 |
| Altertreats Limited | Hackney | 2024 |
| Alteva Composites UK Ltd | London | 2026 |
| Altex Engineering Limited | Calne | 1982 |
| Altex Glazing Systems Limited | Brentwood | 1999 |
| Alteza Ceilings Limited | Greenford | 2021 |
| Altfibr Limited | London | 2025 |
| Altham Fabrications Limited | Blackburn | 2016 |
| Altham Marine Services Ltd | Accrington | 2017 |
| Altham Oak Bespoke Structures Limited | Nelson | 2015 |
| Althams Catering Butchers Limited | Morecambe | 1999 |
| Althams Fine Foods Ltd | Morecambe | 2015 |
| Althon (Contracting) Limited | | 1961 |
| Althorne Marine Services (Mechanical) Limited | Maldon | 2010 |
| ALTI-2 Europe Limited | Ipswich | 2009 |
| Altida Limited | Chesterfield | 2014 |
| Altimex Limited | Chester | 1995 |
| Altin Fashion Style Ltd | London | 2020 |
| Altion Engineering Limited | Tunbridge Wells | 2022 |
| Altiplas Limited | High Wycombe | 2016 |
| Altira Aerotech Limited | Bideford | 2025 |
| Altiski Ltd | Poole | 2026 |