While you are trying to cancel a document, you may receive the following message:
"You cannot issue this Document as there is not enough availability in the inventory location selected for product: [NameOfYourProduct]. Negative stock is not supported. Availability is not updated."
The reason is, you are canceling a document [Purchase Bill/Goods In/Receive on Consignment] that brought in stock which was then shipped/sold.
If you were allowed to cancel this, you would end up with negative stock at some point in history for the items listed in the warning message.
To be able to cancel this document you should cancel the [Sales Invoices/Consignments/Goods Out] document(s) that shipped those items after the [Purchase Bill/Goods In/Receive on Consignment] was issued. After that, you will be able to cancel the [Purchase Bill/Goods In/Receive on Consignment].
Or login to your account.