2 sentences for 凭证 (píng​zhèng — voucher)

1. 请保留好这张发票，作为报销的凭证。

   qǐng bǎo​liú hǎo zhè zhāng fā​piào, zuò​wéi bào​xiāo de píng​zhèng.

   Please keep this invoice as a voucher for reimbursement.

   Source: Dong Chinese Dictionary

2. 请凭这张凭证到行李房提取您的行李。

   qǐng píng zhè zhāng píng​zhèng dào xíng​li​fáng tí​qǔ nín de xíng​li.

   Please present this voucher at the baggage room to pick up your luggage.

   Source: Dong Chinese Dictionary