Website     https://www.gov.uk/veteran-card

See also - Digital version 

An HM Armed Forces Veteran Card is a way to prove that you served in the UK armed forces. The card can make it quicker and easier to apply for support* as a veteran.

*Can only be used as proof of service for Emergency PoS, the card does not give details of service ie: Regiment/Corps and therefore cannot be used as a replacement for full VoS.