The X-report is an interim report of a checkout day. All transactions are recorded in it. Since you can also reopen receipts during the checkout day - e.g. in the case of a return - the turnover is not yet final: The X-report is therefore always an interim report and not tax compliant.
You can open and print the current X-report via [Main menu] > [Reports].
As soon as you close the day in MINI by orderbird by tapping on "End day" or you have programmed an automatic end of day, the sales are finalized and saved in a Z-report.