How it occurred
If you check out a booking, but the invoice total doesn't match the payment total, it could because a billed to agent extra was removed and added back.
For example, doing the following will cause this issue:
Add an extra to the booking and tick "Bill to agent".
Invoice the agent
Add additional extras to the booking
Remove the bill to agent extra
Add the bill to agent extra back again
How to fix
Because the billed to agent was added, removed and added again, Preno will add the extra to the final invoice that is generated.
The billed to agent extra should already be accounted for in the invoice that was created for the agent.
To fix the issue, you will need to edit the invoice that was generated when the booking was checked out and remove the bill to agent extra that was added.
Click into the Xero invoice that was generated.
Remove the payment/prepayment applied to the invoice.
Edit the invoice and remove the billed to agent extra.
Save the invoice and apply the payment or allocate the prepayment back to the invoice.