How to correct accidently charging the owner twice for the same repair and remitting

To correct this will depend on whether you're using Xero or just Arthur. What is required is the undoing of the remittance, making the change and re submitting the remittance   Arthur only

1. Unallocate the remittance in Arthur -
2. Void the transaction and redo the remittance

Xero Only

1. Unallocate the remittance in Xero and sync
2. Void the transaction. At this point, any changes can be done on either account and synchronization will once again make changes to both.