You can easily change the upcoming bill dates for a membership by following the steps below:
Search for and select the patient
Select their 'Memberships' tab
Click on the existing membership to edit it
In the 'Summary' section of the membership page, click 'Change Billing Date'
Enter the desired date
Click 'Update' at the bottom of the page to save the change.
This will update the membership's next bill due date and all future bills will follow the updated billing schedule accordingly.