OneSaas consolidates all sales and refunds of a day in a single summary while also grouping the payments by the method name. Due to refunds it is possible that the end of day summary contains more refunds than sales (by method type).
When there are more refunds then sales on a payment method, OneSaas will generate a separate summary to represent only the negative payments (refunds). This should allow for easy reconciliation of the daily summary against your bank account.
$100 Sale paid $50 from EFTPOS and $50 Cash
-$200 Refund on EFTPOS
The total sales for the day is –$100 made out of $50 CASH and –$150 EFTPOS. However generating such a summary would not be compatible with most accounting systems if you will try to record the two payments on the daily summary.
For this OneSaas will use an intermediate Negative Payments Account to allow the split of the negative part from the daily summary into a separate summary.

Daily Summary #1 records the Total Sales of –$100 and the $50 CASH payment while also recording $150 into the Negative Payments Account moved into the separate refund invoice.
Daily Summary #2 records the negative part of the daily summary of -$150 EFTPOS reducing it back from the Negative Payments Account.
Using the intermediary Negative Payments Account has no effect on your P/L because the transactions are already recorded in pairs on the same day.