It is sale entry for that item with zero or reduced price. If item is completely spoiled and cannot be sold then make usual sale invoice entry right when item is spoiled or comes to notice. The listed price will come automatically. You will manually replace the price with 0. Furthermore, you will also manually edit the ‘explanation’ of that sale invoice. For a normal sale entry, there is no need to enter ‘explanation’ because it is automatically written by the system. But for a spoiled or wasted item’s entry, ‘explanation’ should be manually modified.
If wasted product is sold at reduced price then make this entry at the time of sale. The effect of sale invoice entry with zero or reduced price will be that the entry will be reflected as ‘loss’ in relevant reporting.