Hello Edward,

1. You must be running Adagio Receivables V9.0A if you want to use Adagio Invoice 9.0A. Upgrading Adagio Receivables from V8.1 to 9.0 is a fairly involved process and should be undertaken on a copy of the data before doing so in a live environment.
2. Adagio Invoices has always been compatible with Adagio Inventory. Sales recorded on invoices are sent to Inventory using a Shipment batch which is retrieved and posted. There is an option in the Invoices company profile whether to adjust the on-hand quantities displayed on an item inquiry by the quantities recorded in Arcive batches, if you are looking for more up to date on-hand statistics. Were you looking for something in particular?
3. Adagio Invoices does not permit credit notes to return items to inventory as Doug mentioned. It is good practice to separate out credit notes from invoices into separate batches. They sould have their own numbering conventions as well.

Good luck with the upgrade!