How do I detect a refund? (question about cancellation_date)

How do I detect a refund? (question about cancellation_date)

My system uses auto-renewal subscriptions.
After reading this document:
https://developer.apple.com/library/archive/technotes/tn2413/_index.html#//apple_ref/doc/uid/DTS40016228-CH1-RECEIPT-HOW_DO_I_USE_THE_CANCELLATION_DATE_FIELD_
I am not sure about how to manage the refund scenario.

The docs say that I have to check cancellation_date field. But what I don’t know is WHEN I will receive that.

When the user requests a refund to apple and apple accepts it, will my app receive a new transaction in 

Code Block 
func paymentQueue(_ queue: SKPaymentQueue, 
updatedTransactions transactions: [SKPaymentTransaction])

the next time the user runs the app?

Or do I have to use polling (my server checks every day with apple server all subscribers) or use server-to-server notifications?

Thanks for clarification.