Hi,
In this case you need to use POD ( Proof of delivery ) concept for your customer. Where you can't create invoice after doing POD with tcode VLPOD.
There need some more config to follow.
1:- Need to activate at POD relevant for item category.
2:- Need to activate "Relevant for POD"at customer master Sales area Shipping tab.
3:-Need to maintain Reason for Variance in POD (like DFG1 & DFG2)
Hope it will help you.
Regards
Pitabash