How do I know which Retailers allow cancellations?
You can find this in the Brand details section of the Hub, for example:
It is also important to note that some retailers only allow cancellations for a small window. For example Amazon allow cancellations only in the first 15 minutes post sale.
How do I cancel?
There are two options, either via the API or from within the Partner Hub
Via the Partner Hub: https://teamtillo.zendesk.com/hc/en-gb/articles/7459914316317
What if the Brand/Retailer does not support cancellations?
You can always get in contact with the retailer to see if they will process the cancellation. If they agree make sure they mark the order as cancelled in the Hub so that your reporting is correct.