XERO comes with a powerful payroll software which handles automated taxes, pay and super. Bit.leave mainly leverages the payroll components in XERO to fetch organisation settings, employee information and payroll related data including leave types and balances.
Please refer to the video and material on XERO Setup doc. This will cover the steps on user flow and permissions necessary to make bit.leave work with your XERO data.
bit.leave uses a popular middleware (StackGO) to communicate to and from XERO. Once the setup is done (as above), bit.leave fetches data from XERO using the XERO's Payroll APIs.