CRA has recently released two new videos as part of their Gifting and Receipting video series. These videos are as follows: Auctions: when you can issue donation receipts and Auctions: advantage and 80% rule.  

The CRA videos can be found here: https://www.canada.ca/en/revenue-agency/news/cra-multimedia-library/charities-video-gallery/charities-giving-series-gifting-receipting.html or on CRA's YouTube Channel