According to docs price increases will create a prorated transaction:
If you increase the price and have proration enabled, we will create a prorated transaction based on the change in price for the remainder of the billing cycle. If you decrease the price, the change will take effect in the next billing period. Proration can be configured for use with upgrades and / or downgrades.
Is there a way to track decreases in price as they don't seem to appear in transactions but affect balance?
What happens with the negative balance in case of a cancelation?
I work at Braintree. If you have more questions, feel free to get in touch with our support team.
Is there a way to track decreases in price as they don't seem to appear in transactions but affect balance?
If you look at the subscription in the control panel, you will see a skipped transaction when we would have charged the subscription but the balance was negative or zero.
If the subscription was previously active (not necessarily when it was past due) you can also tell a prorated downgrade was applied because the balance will be negative.
What happens with the negative balance in case of a cancellation?
The subscription will be canceled with a negative balance. If you have webhooks set up, you can see this on the subscription sent with the SubscriptionCanceled webhook.