This version shared with the customers should ONLY be installed in the Sandbox. This should not be installed in the production org until announced.
make sure that the Legal entity has valid accounting periods
enable Delta invoicing on the Admin settings
Edit layouts to add new fields of the campaign items, invoices, and invoice items
remove all processes that call the delivery data update function on the invoice object
if you use an optimizer - remove the processes that set the default optimization source and cancelation modes
Remove everything that calls preinvoice generation after optimizing version optimization
if you want to test campaign item in-field editing - disable the feature setting “Prevent field changes”
new Delta Preinvoice generation - run preinvoice generation for all your campaign combinations, payment intervals, flexible payment plans, timesheet activities, and invoice contacts. All the billing process
how the pre-invoice items are merged into preinvoices, based on the runtime, intervals, and the accounting period status
validate the campaign item billing status and the campaign item invoiced amount
If you use Landscape PDF - check the layout
Validate process and recalculation of the Published payout
Ask your admin checking the Mapping BA custom settings, if there are only default values, those can be cleaned up. If there are custom settings created by your admin, those should be validated
Please read what comes in the next Delta release to have a correct expectation.