| Altemis Ltd | Dedham | 2002 |
| Altemislab Ltd | Cambridge | 2018 |
| Alten Ltd | London | 2013 |
| Alten Strategic Limited | London | 2014 |
| Altenergis PLC | London | 2011 |
| Alteo EXP Limited | London | 2021 |
| Alteoy Ltd | Dormansland | 2024 |
| Alter Agency Ltd. | Milton Keynes | 1994 |
| Alter Eco Communications Ltd | Witney | 2011 |
| Alter Lingo Limited | Lowestoft | 2010 |
| Alter Results CIC | Plymouth | 2023 |
| Alter Services Ltd | Wimborne | 2018 |
| Alter Studio Ltd | Arnside | 2021 |
| Alter&Company Ltd | Brighton | 2016 |
| ALTER-N8TIVE-SPACES Ltd | Stoke-On-Trent | 2025 |
| Alter-Projects Limited | London | 2015 |
| Altera Consulting Ltd | London | 2023 |
| Altera Product Ltd | Chigwell | 2025 |
| Altera Projects Ltd | Nottingham | 2025 |
| Altera Services Ltd | London | 2017 |
| ALTERA2ION Labs Ltd | London | 2026 |
| Alteratio Limited | Bolton | 2013 |
| Alteration + Repair Architects Ltd | London | 2025 |
| Alterations Specialist Ltd | Manchester | 2023 |
| Alterbloom Ltd | Thornton Heath | 2026 |
| Altercroft Ltd | Bradford | 2026 |
| Alterd Ltd | Bath | 2020 |
| Alterdyne Global Services Ltd | London | 2020 |
| Altered Carbon Limited | Bristol | 2018 |
| Altered Image Property Consultants Limited | Swanley | 2014 |
| Altered Images Photography Limited | Rotherham | 2008 |
| Altered Nation Design Ltd | London | 2005 |
| Altered States Marketing Limited | Durley | 2023 |
| Alteregoglobal Limited | London | 2009 |
| Alterevo Ltd | London | 2014 |
| Altergaze Ltd | London | 2014 |
| Alterian Holdings Limited | Maidenhead | 2006 |
| Alterian Software Limited | London | 2016 |
| Alterion Consulting Limited | Maidstone | 2010 |
| Alterion Group Ltd | London | 2026 |
| Alterior Living Limited | Horsham | 2022 |
| Alterity Business and Academic Services Limited | Glasgow | 2014 |
| Alterity Global Ltd | London | 2018 |
| Alterity Therapeutics UK Limited | Cambridge | 2004 |
| Alterix Limited | Cambridge | 2003 |
| Alterjective Limited | King'S Lynn | 2011 |
| Alterkind Ltd | Hebden Bridge | 2017 |
| Alterledger Ltd | Glasgow | 2012 |
| Altermans Solicitors Limited | London | 2014 |
| Altermata Ltd | Birmingham | 2024 |
| Alterme Limited | London | 2020 |
| Altermind UK Limited | London | 2012 |
| Altermont Limited | London | 2023 |
| Altern Solutions Ltd | Leamington Spa | 2025 |
| Alternate Current Publicity Limited | Harrow | 2020 |
| Alternate Ending's Limited | Hampshire | 2002 |
| Alternate Legal Services Limited | Bury St. Edmunds | 2021 |
| Alternate Media Limited | Cardiff | 2018 |
| Alternate Paradigms Limited | London | 2017 |
| Alternateam Ltd | London | 2025 |
| Alternatev Ltd | Manchester | 2019 |
| Alternating Solutions Ltd | Derry | 2024 |
| Alternation Projects Ltd | Shepperton | 2015 |
| Alternative Accounts Ltd | Bolton | 2025 |
| Alternative Advertising Limited | Bristol | 2002 |
| Alternative Angles Business Consultancy Limited | Yeovil | 2001 |
| Alternative Automotive Media Limited | Newport | 2015 |
| Alternative Avenue Ltd | London | 2017 |
| Alternative Building Control Solutions Limited | Wirral | 2001 |
| Alternative Business School Ltd | Warwick | 2018 |
| Alternative Choices Limited | Huddersfield | 2009 |
| Alternative Consulting Limited | London | 2025 |
| Alternative Contract Solutions Limited | Chichester | 1977 |
| Alternative Costs Ltd | Cardiff | 2014 |
| Alternative Credit Advisers Limited | London | 2017 |
| Alternative Dispute Resolution Services Limited | Newcastle Upon Tyne | 1999 |
| Alternative Element (Holdings) Ltd | London | 2014 |
| Alternative Energy Consulting Ltd | London | 2025 |
| Alternative Energy Group Ltd | Pinner | 2021 |
| Alternative Energy Services Ltd | Upminster | 2019 |
| Alternative Energy Technologies Limited | Royal Leamington Spa | 2018 |
| Alternative Energy Ukraine Ltd | Bridgwater | 2017 |
| Alternative Equity Limited | Cannock | 2023 |
| Alternative Equity Two Limited | Cannock | 2024 |
| Alternative Finance Solutions Limited | Portsmouth | 2015 |
| Alternative Financial Advice Limited | Driffield | 2020 |
| Alternative Fuels Incorporated Limited | Leatherhead | 2015 |
| Alternative Future Ltd | Thames Ditton | 2017 |
| Alternative Futures Consulting Limited | Glasgow | 2022 |
| Alternative Global Solutions Ltd | Birmingham | 2014 |
| Alternative Illustrated Limited | Blackpool | 2024 |
| Alternative Infrastructure Investments Limited | Harrow | 2009 |
| Alternative Inspection Limited | Bury St. Edmunds | 2020 |
| Alternative Investment Index Ltd | Herts | 2007 |
| Alternative Investment Management Ltd | London | 2019 |
| Alternative Investments Consulting Ltd | London | 2019 |
| Alternative Journey Ltd | Woodford Green | 2020 |
| Alternative Leaders Ltd | London | 2018 |
| Alternative Learning Initiative Group Network CIC | Southsea | 2026 |
| Alternative Legal Limited | Harrow On The Hill | 2019 |