Doubleclick Bid Manager, the buying tool from Doubleclick in programmatic, will refund Advertisers of invalid ads on the supply chain. That is one of 3 measures to fight spam and fraud on programmatic, announced by Doubleclick/Google on 21st September.
In the blog post, Google says that AppNexus, Index Exchange, OpenX, Pubmatic, SpotX, Teads, Telaria and DoubleClick Ad Exchange have been very supportive of these changes and have committed to provide advertisers with refunds for invalid traffic detected up to 30-days after monthly billing. These agreements/commitments represent 90% of the buying activity on programmatic.
A news on this topic is that Bid Manager will show which supply partners provide refunds for invalid traffic and offer advertisers the option to buy only from those sources. So the Exchanges that do not support refunds over invalid traffic will be under pressure from Advertisers.
See here how Google provide transparency on the invalid traffic and how Google will support Ads.txt on Bid Manager.