Link should work now! ) in wrong place - sorry!
Renewal is the action required when something has lapsed
Revalidation is the action taken to maintain validity
Technically, a licence is 're-issued' - some numpty at the CAA cocked up the description. There is NO test, you just fill in the form showing your Rating validity dates etc. But you must have a valid aircraft Class (or Type) Rating as well as a valid medical certificate.
So, last year I
revalidated my Medical, SEP Class Rating, IMC Rating and FI Rating and was
reauthorised as an Examiner; this year I need to have my licence
reissued.
Simple, really...........