Entering 3 way match invoices when there is no Receipt

Our users are currently using 2 way match.  They realize 3 way match provides tigher controls and want to switch.  However we've told them the invoice can not be entered until the receipt occurs. 

We do not have a good culture for completing receipts on time.  There are no consequences if items are not received, so often they are not.   Invoices frequently arrive and become past due before receipt is done.Questions:Did we give the correct information to the users?What process are other companies using to encourage/require receipts to be completed timely?If AP just keeps the stack of unreceipted invoices on their desk (as ours is doing today) how can AP be notified that receipt has occured and they can now enter and pay the invoice?