Most sales reports are based on "order data" and order date.
This means, that by default, unpaid orders are included in the reports, as many merchants accept orders without payment (for payment on account). There is usually a tick box for those who wish to limit the report to only paid orders.
The information is summarised by the date the order was placed, and not the date the order was paid (if different). Even if you restrict to paid orders, the reports are summarised by the order date.
If an order is cancelled, then it will be removed from the report (and historical reports if reprinted). Cancelled orders also replenish stock counts.
The exception to this cancellation rule is when the report is specifically a payment summary, where we continue to include receipts (and refunds) from cancelled orders, as this was the true monetary flow of the time. The date the money was received, and the date any money was refunded.
Various merchants have asked us to add features/columns to the reports over time, and these may be confusing for other users. If you have any confusion around the meaning of a report data metric, please ask support. However, please note that all support time explaining reports is considered consultancy (chargeable time). It's not always as easy answer to explain the auditable depth of the calculations involved, and every merchant/user has a different expectation.