Yep just need it for issue. so its a good thing to do as part of your hour building really, cracks off a good few hours in a day and its P1 time.
I did however keep the landing receipts at the 2 airfields i went to as proof i went there to go along with the log book entry, and my club runs PPL qualifier forms that the ATCOs have to sign, they edited one for me for the CPL qualifier.
So i have it in my log book, 2 receipts (dated) and a form signed by the two ATC officers at the 2 aerodromes i visited.
Just a piece of adive - make sure its 300nm as the crow flies (direct) as thats the way the CAA measure it.