NickB

Is there? There is not any magic format or words that need to be used to make something a "certificate". A document that officially records some information is entirely capable of certifying something even if the word "certificate" is not used anywhere. Indeed, the pdf that you get from NHS digital when you request a print out or email version does not use the word certificate either. It uses the terminology of "record" as well. If it is accepted by Spanish authorities as sufficient to establish that the passenger has been vaccinated, then it is a document certifying vaccination as far as the Spanish authorities are concerned.

Whichever way one looks at it, the OP had the correct documentation required to enter Spain and was, therefore, improperly denied boarding. Whatever is or is not on Timatic is neither here nor there. Timatic is not an official statement of enty requirements. It is merely a tool used by airlines to facilitate their task in attempting to ascertain what those requirements are. It has no authoritative value.