Money & WorkFact
In year one, the seller has to prove it, not you.
Normally the person claiming a defect must prove it was there all along. The EU Sale of Goods Directive flips that: if the fault shows up within one year of delivery, it is presumed to have existed at delivery, and the seller must show otherwise.
Useful: That is why the date you report a fault matters: after twelve months the burden of proof lands on you.
Source: eur-lex.europa.eu