Notifications on transactions are pretty useful for checking you were charged the right amount, and how much you’ve spent so far today.
However delayed transactions aren’t as helpful. You can’t deal with it immediately and you aren’t in the shop to query it.
You’ll never get rid of delayed transactions, as an example, TFL charges, which can be a day or two later.
I propose that delay transaction notifications should be silent.
You should still get a notification, but no sound or vibration should occur.
Example: I travel on the underground, TFL charges me two days later. I hear nothing. I feel nothing. But the next time I unlock my phone, or go to my notifications, I can see my TFL transaction.
Technically its feasible, if you remove the sound key from the payload of a delayed transaction push notification, you won’t get any sound or vibration.