Refunding a Contribution that has Sales Tax associated produces Validation Error
Trying to isolate / reproduce some issues with Sales Taxes breaking them down into small bits; this is on 5.3.0
Add Contribution $100 -> Financial Type has Sales Tax associated with it 5% -> Contribution gets recorded as $105 (correctly):
Edit -> change Contribution Status -> from Completed to Refunded -> hit Save;
Net Amount really is $105 and Fee Amount really is $0 - changing them to anything else would be incorrect.
See https://github.com/civicrm/civicrm-core/pull/9948 for original discussion