proof of purchase

基本解释

Researchers asked music buyers to prove that they had proof of purchase.
他们要求所有购买音乐的用户都要出具他们的购买证明。
Apple has reviewed your proof of purchase and your request to update the purchase date in our records.
苹果已经审核了您的购买证明和您的要求来更新我们的记录购买日期。
Please note that your name has to be clearly readable and that we can't process requests without proper proof of purchase.
请注意，您的名字都必须有明确可读，我们无法处理不正确的购买证明的要求。

They are notorious of not servicing something if they do not have the original proof of purchase.
ENGADGET: HDTV Buying Guide: Extended Warranties HD
It comes with a signed box and a copy of proof of purchase from Harry Winston, dated May 23, 1980.
FORBES: 30.52-ct. emerald-cut diamond sold for $3.3 million.
That liability usually ends up as Treasury debt parked at the Federal Reserve in custody for foreign governments, the proof of purchase for billions of dollars in extra U.S. imports.
FORBES: Congress Messes With China While Sen. DeMint Eyes The Dollar