Start with the source transaction, not a generic VAT percentage
Products, shipping and discounts can have different tax treatment. The accounting bridge should retain enough source information to map each component to the correct Xero tax rate and nominal account.
Refunds are new accounting events
A refund on Thursday for a sale made Monday should retain Thursday's refund date and the original order reference. Rewriting Monday's imported figures makes audit history and gateway reconciliation harder to follow.
Shipping and discounts need explicit rules
These amounts should not disappear inside a single unexplained sales figure when the business needs them in separate Xero accounts or tax treatments.
Rounding belongs in a controlled place
When aggregated lines need a minor balancing adjustment to reproduce exact source totals, the rounding rule and account should be configured rather than hidden inside another line.
