Here is a tip that you can do with our point of sale software that one of our clients is doing.
When you pack a parcel to send off to a customer, lay the goods out and take a picture with your smartphone. Then attach this picture to the invoice in the POS System. That way you will have a photo ID of what was sent.
After being burnt badly, this client is now doing it religiously as he states photos is one piece of evidence that the authorities do accept.