| Altech Assist Ltd | Ilford | 2024 |
| Altech Consultancy Limited | Walton On Thames | 2019 |
| Altech Services Ltd | Leamington Spa | 2019 |
| Altech Software Limited | Cwmbran | 2005 |
| Altechnology Limited | Altrincham | 2014 |
| Altechto Limited | Coventry | 2026 |
| Altegic Ltd | London | 2020 |
| Altelium Ltd | Leeds | 2018 |
| Alten Technology UK Limited | London | 2019 |
| Altenar Software Limited | Radlett | 2020 |
| Alter Aspect Ltd | Eastbourne | 2026 |
| Alter Domus Data Solutions (UK) Limited | London | 2016 |
| Alter EGO Music Group Ltd | Leamington Spa, | 2016 |
| Alter EGO Technologies Ltd | London | 2023 |
| Alter Horizon Enterprises Limited | Southampton | 2017 |
| Alter Labs Ltd | London | 2025 |
| Alter Menta Technologies Ltd | London | 2026 |
| Alter Motion Creative Ltd | Sutton | 2021 |
| Altera Digital Ltd | London | 2026 |
| Altera Global Inc Ltd | London | 2025 |
| Altera Partners Limited | London | 2000 |
| Altera Semiconductor Technology UK Limited | London | 2023 |
| Altera Wealth Insights Limited | Hatch End | 2023 |
| Alteracore Ltd | Dumfries | 2025 |
| Alteratech Solutions Ltd | South Croydon | 2025 |
| Alteration by Linda Ltd | Greenock | 2026 |
| Alterativus Limited | Whyteleafe | 2004 |
| Alteravox Ltd | Newry | 2009 |
| Alterbybyte Ltd | London | 2025 |
| Alterdd Ltd | Peterborough | 2025 |
| Altere Ltd | London | 2020 |
| Altered Aspect VFX Limited | Potters Bar | 2020 |
| Altered Creations Limited | Ashford | 2021 |
| Altered Dimension Ltd | Exeter | 2025 |
| Altered Gene Limited | Broadstairs | 2013 |
| Altered Image Films Ltd | Llwyngwril | 2007 |
| Altered Ltd | London | 2018 |
| Altered Matrix Limited | Preston | 2025 |
| Altered Move Ltd | Bridgwater | 2021 |
| Altered Packet Limited | Trowbridge | 2013 |
| Altered Perceptions Limited | | 1996 |
| Altered Self Limited | Reading | 2012 |
| Altered State PMA Ltd | Bolton | 2013 |
| Altered States FX Limited | Weybridge | 2013 |
| Altered States Technologies Ltd | Prenton | 2021 |
| Altered TV Limited | London | 2013 |
| Altered Visuals Ltd | Richmond | 2025 |
| Alterego Media Limited | Stratford-Upon-Avon | 2019 |
| Alterego Technology Ltd | Wembley | 2019 |
| Alterem Consulting Ltd. | Ilford | 2013 |
| Alterest Limited | London | 2015 |
| Altergaia Limited | Warwick | 2018 |
| Altergrafx Ltd | London | 2025 |
| Altergroup Limited | Ruislip, | 2024 |
| Alterian Technology Limited | Maidenhead | 1997 |
| Altering Ltd | East Grinstead | 2024 |
| Alteris Software Consultancy Ltd | Burnley | 2021 |
| Alterity Arts Ltd | London | 2019 |
| Alterius Systems Limited | Leicester | 2011 |
| Altermeliora Limited | West Malling | 2021 |
| ALTERN8 Limited | Bristol | 1998 |
| ALTERN8 Solutions Ltd | London | 2018 |
| Alternate Associates Ltd | | 1998 |
| Alternate Digital Ltd | Reading | 2026 |
| Alternate Hypothesis Limited | Gloucester | 2025 |
| Alternate IT Solutions Limited | Oldham | 2008 |
| Alternate Labs Ltd | Belfast | 2014 |
| Alternate Reality Media Ltd | London | 2025 |
| Alternate Software Limited | Penarth | 2026 |
| Alternate States Ltd | Heywood | 2018 |
| Alternatepress Limited | Pinner | 2012 |
| Alternatexr Ltd | London | 2026 |
| Alternative Blueprint Limited | Taunton | 2008 |
| Alternative Broadcast Company | Stoke On Trent | 2016 |
| Alternative Business Funding Limited | Bristol | 2014 |
| Alternative Care Systems Ltd | St. Asaph | 2025 |
| Alternative Comms Limited | Witney | 2014 |
| Alternative Communication Systems Limited | Witney | 2014 |
| Alternative Communications and Media Ltd | Mitcham | 2017 |
| Alternative Content Limited | Fair Oak | 2012 |
| Alternative Derivatives Exchange Ltd | London | 2018 |
| Alternative Edge Media Ltd | Liverpool | 2023 |
| Alternative Endings Productions Ltd | Brighton | 2014 |
| Alternative Events Limited | Christchurch | 2016 |
| Alternative Facts Records Limited | Carlisle | 2020 |
| Alternative Film-Marketing Company Limited | London | 2012 |
| Alternative Films Limited | Dunstable | 2023 |
| Alternative Fuel Infrastructure Ltd | London | 2025 |
| Alternative Integration Solutions Limited | Solihull | 2025 |
| Alternative Investment Consultants Ltd | Walton-On-Thames | 2020 |
| Alternative Investment Partners Limited | London | 2017 |
| Alternative Investment Technologies Ltd | London | 2019 |
| Alternative Laboratory Ltd | Bracknell | 2025 |
| Alternative Living Ltd | Stranraer | 2020 |
| Alternative Logic (UK) Limited | Deeside | 2003 |
| Alternative Logic Limited | Deeside | 2001 |
| Alternative Media Group PLC | London | 2026 |
| Alternative Movie Posters Ltd | London | 2015 |
| Alternative Real Estate Investments Limited | Tring | 2019 |
| Alternative Realities Limited | Exeter | 2016 |