Has it had all the work done at VW? If so ring them up tell them your thinking of servicing the car there even if your not, give them the reg and they should tell you everything they can about the car. That's what I did
He's only had it 5 months so if there's been no work done then no invoices will be relevant.
My VW service book has spaces for timing belt and tensioners. I phoned VW up in regard to my sons car and they confirmed his belt had been changed by them on a previous service. If in doubt chage it, had one snap before, once bitten twice shy.