Hello,
When it comes to the Sales Module, there are actually two modules in Sales. Three Technically but Invoicing Module will not be part of this response.
In Sales you have the Sales Order Processing, and you have the Receivables Management. The Posted Transactions window is for the Receivables Modules. For Sales Order Processing, we do not have a window to void a posted Sales Order Processing Transaction. We can only Void a Sales Transaction before it was voided.
With the information that was provided in the questions, if you void a Sales Invoices from SOP in the Posted Transactions window, you only voided the Receivables Document that gets created when posting a Sales Invoice. This does not do anything with your Inventory.
The correct way to "Void" a Sales Order Process Invoices and have Inventory adjusted as well would be to do a Sales Order Processing Return.
Below is a link to the Sales Order Processing PDF for Dynamics GP.
If you need to adjust your Inventory now due to the void, you could try the following. I suggest in test to verify the outcome first.
1. Adjust Inventory to put the quantity back.
Another option:
1. Recreate the Receivables documents that was voided.
2. Process a Return in Sales Order Processing.
3. Apply the Return to the Invoices in Receivables Management.
4. Verify this solves your issue.
I hope this helps!
Brandon - Enavate.