There are different types of syncs that happen between Re-Leased and Xero that happen under different circumstances and at different times.
Automatic sync will happen every night. This will synchronise all data between Xero and Re-Leased.
If a change is made to data in Re-Leased, then it will be pushed to Xero immediately. For instance, if an Invoice is added or if a Contact is updated then Re-Leased will push it to Xero immediately.
You can also force a manual sync, go to the Settings menu, then Manage Add-ons and select Xero. You can force all data to be synchronised or just certain data elements.
IMPORTANT NOTE: there is a 1:1 connection between each Re-Leased company and the corresponding Xero company. Once a Re-Leased company has been connected to a Xero company, it cannot be re-connected to any other Xero company.